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Psychedelics are a subclass of hallucinogenic drugs whose primary effect is to trigger non-ordinary mental states (known as
psychedelic experience A psychedelic experience (known colloquially as a trip) is a temporary altered state of consciousness induced by the consumption of a psychedelic substance (most commonly Lysergic acid diethylamide, LSD, mescaline, psilocybin mushrooms, or N,N- ...
s or "trips") and a perceived "expansion of consciousness". Also referred to as classic hallucinogens or serotonergic hallucinogens, the term ''psychedelic'' is sometimes used more broadly to include various other types of hallucinogens as well, such as those which are atypical or adjacent to
psychedelia Psychedelia usually refers to a Aesthetics, style or aesthetic that is resembled in the psychedelic subculture of the 1960s and the psychedelic experience produced by certain psychoactive substances. This includes psychedelic art, psychedelic ...
like
salvia ''Salvia'' () is the largest genus of plants in the sage family Lamiaceae, with just under 1,000 species of shrubs, Herbaceous plant, herbaceous Perennial plant, perennials, and Annual plant, annuals. Within the Lamiaceae, ''Salvia'' is part o ...
and
MDMA 3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor Psychedelic drug, psychedelic properties. In studies, it has been used ...
, respectively. Classic psychedelics generally cause specific psychological,
visual The visual system is the physiological basis of visual perception (the ability to detect and process light). The system detects, transduces and interprets information concerning light within the visible range to construct an image and buil ...
, and auditory changes, and oftentimes a substantially altered state of consciousness. They have had the largest influence on science and culture, and include
mescaline Mescaline, also known as mescalin or mezcalin, and in chemical terms 3,4,5-trimethoxyphenethylamine, is a natural product, naturally occurring psychedelic drug, psychedelic alkaloid, protoalkaloid of the substituted phenethylamine class, found ...
, LSD,
psilocybin Psilocybin, also known as 4-phosphoryloxy-''N'',''N''-dimethyltryptamine (4-PO-DMT), is a natural product, naturally occurring tryptamine alkaloid and Investigational New Drug, investigational drug found in more than List of psilocybin mushroom ...
, and DMT. There are a large number of both
naturally occurring A natural product is a natural compound or substance produced by a living organism—that is, found in nature. In the broadest sense, natural products include any substance produced by life. Natural products can also be prepared by chemical ...
and synthetic serotonergic psychedelics. Most psychedelic drugs fall into one of the three families of chemical compounds: tryptamines, phenethylamines, or lysergamides. They produce their psychedelic effects by binding to and activating a
receptor Receptor may refer to: * Sensory receptor, in physiology, any neurite structure that, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and respond ...
in the
brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...
called the
serotonin Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...
5-HT2A receptor. By activating serotonin 5-HT2A receptors, they modulate the activity of key circuits in the brain involved with sensory perception and cognition. However, the exact nature of how psychedelics induce changes in perception and cognition via the serotonin 5-HT2A receptor is still unknown. The psychedelic experience is often compared to non-ordinary forms of consciousness such as those experienced in
meditation Meditation is a practice in which an individual uses a technique to train attention and awareness and detach from reflexive, "discursive thinking", achieving a mentally clear and emotionally calm and stable state, while not judging the meditat ...
,
mystical experience A religious experience (sometimes known as a spiritual experience, sacred experience, mystical experience) is a subjective experience which is interpreted within a religious framework. The concept originated in the 19th century, as a defense ag ...
s, and
near-death experience A near-death experience (NDE) is a profound personal experience associated with death or impending death, which researchers describe as having similar characteristics. When positive, which the great majority are, such experiences may encompa ...
s, which also appear to be partially underpinned by altered
default mode network In neuroscience, the default mode network (DMN), also known as the default network, default state network, or anatomically the medial frontoparietal network (M-FPN), is a large-scale brain network primarily composed of the dorsal medial prefro ...
activity. The phenomenon of
ego death Ego death is a "complete loss of subjective self-identity". The term is used in various intertwined contexts, with related meanings. The 19th-century philosopher and psychologist William James uses the synonymous term "self-surrender", and Jung ...
is often described as a key feature of the psychedelic experience. Many psychedelic drugs are illegal to possess without lawful authorisation, exemption or license worldwide under the UN conventions, with occasional exceptions for religious use or research contexts. Despite these controls, recreational use of psychedelics is common. There is also a long history of use of naturally occurring psychedelics as entheogens dating back thousands of years. Legal barriers have made the scientific study of psychedelics more difficult. Research has been conducted, however, and studies show that psychedelics are physiologically safe and rarely lead to
addiction Addiction is a neuropsychological disorder characterized by a persistent and intense urge to use a drug or engage in a behavior that produces natural reward, despite substantial harm and other negative consequences. Repetitive drug use can ...
. Studies conducted using psilocybin in a psychotherapeutic setting reveal that psychedelic drugs may assist with treating depression,
anxiety Anxiety is an emotion characterised by an unpleasant state of inner wikt:turmoil, turmoil and includes feelings of dread over Anticipation, anticipated events. Anxiety is different from fear in that fear is defined as the emotional response ...
, alcohol addiction, and nicotine addiction. Although further research is needed, existing results suggest that psychedelics could be effective treatments for certain mental health conditions. A 2022 survey by
YouGov YouGov plc is a international Internet-based market research and data analytics firm headquartered in the UK with operations in Europe, North America, the Middle East, and Asia-Pacific. History 2000–2010 Stephan Shakespeare and Nadhim ...
found that 28% of Americans had used a psychedelic at some point in their life.


Examples

* LSD (lysergic acid diethylamide) is a derivative of lysergic acid, which is obtained from the
hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...
of ergotamine. Ergotamine is an
alkaloid Alkaloids are a broad class of natural product, naturally occurring organic compounds that contain at least one nitrogen atom. Some synthetic compounds of similar structure may also be termed alkaloids. Alkaloids are produced by a large varie ...
found in the fungus '' Claviceps purpurea'' (ergot), which primarily infects rye. LSD is both the prototypical psychedelic and the prototypical lysergamide. As a lysergamide, LSD contains both a tryptamine and phenethylamine group within its structure. Uniquely among psychedelics, LSD agonises dopamine receptors as well as serotonin receptors. * Psilocin (4-HO-DMT) is the dephosphorylated active metabolite of the indole alkaloid
psilocybin Psilocybin, also known as 4-phosphoryloxy-''N'',''N''-dimethyltryptamine (4-PO-DMT), is a natural product, naturally occurring tryptamine alkaloid and Investigational New Drug, investigational drug found in more than List of psilocybin mushroom ...
and a substituted tryptamine, which is produced by hundreds of species of psilocybin-containing mushrooms. Of the classical psychedelics, psilocybin has attracted the greatest academic interest regarding its ability to manifest mystical experiences, although all psychedelics are capable of doing so to variable degrees. 4-AcO-DMT (''O''-acetylpsilocin or psilacetin) is a synthetic acetylated analogue of psilocin and is a prodrug of psilocin similarly to psilocybin. *
Mescaline Mescaline, also known as mescalin or mezcalin, and in chemical terms 3,4,5-trimethoxyphenethylamine, is a natural product, naturally occurring psychedelic drug, psychedelic alkaloid, protoalkaloid of the substituted phenethylamine class, found ...
(3,4,5-trimethoxyphenethylamine) is a phenethylamine alkaloid found in various species of cacti, the best-known of these being peyote (''Lophophora williamsii'') and the San Pedro cactus (''Trichocereus macrogonus'' var. ''pachanoi'', syn. ''Echinopsis pachanoi''). Mescaline has effects comparable to those of LSD and psilocybin. Ceremonial San Pedro use seems to be characterized by relatively strong spiritual experiences, and low incidence of challenging experiences. * DMT (''N'',''N''-dimethyltryptamine) is an indole alkaloid found in various species of plants. Traditionally, it is consumed by tribes in
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
in the form of ayahuasca. A brew is used that consists of DMT-containing plants as well as plants containing MAOIs, specifically harmaline, which allows DMT to be consumed orally without being rendered inactive by
monoamine oxidase Monoamine oxidases (MAO) () are a family of enzymes that catalyze the oxidation of monoamines, employing oxygen to clip off their amine group. They are found bound to the outer membrane of mitochondria in most cell types of the body. The fi ...
enzymes in the digestive system. A pharmaceutical version of ayahuasca is called pharmahuasca. In the Western world, DMT is more commonly consumed via the vaporisation of freebase DMT. Whereas ayahuasca typically lasts for several hours, inhalation has an onset measured in seconds and has effects measured in minutes, being much more intense. Particularly in vaporised form, DMT has the ability to cause users to enter a hallucinatory realm fully detached from reality, being typically characterised by
hyperbolic geometry In mathematics, hyperbolic geometry (also called Lobachevskian geometry or János Bolyai, Bolyai–Nikolai Lobachevsky, Lobachevskian geometry) is a non-Euclidean geometry. The parallel postulate of Euclidean geometry is replaced with: :For a ...
, and described as defying visual or verbal description. Users have also reported encountering and communicating with entities within this hallucinatory state. DMT is the archetypal substituted tryptamine, being the structural scaffold of psilocybin and, to a lesser extent, the lysergamides. * 2C-B (2,5-dimethoxy-4-bromophenethylamine) is a
substituted phenethylamine Substituted phenethylamines (or simply phenethylamines) are a chemical class of organic compounds that are based upon the phenethylamine structure; the class is composed of all the derivative (chemistry), derivative compounds of phenethylamine ...
first synthesized in 1974 by Alexander Shulgin. 2C-B is both a psychedelic and a mild
entactogen Entactogens, also known as empathogens or connectogens, are a class of psychoactive drugs that induce the production of experiences of emotional communion, oneness, connectedness, emotional openness—that is, empathy—as particularly observe ...
, with its psychedelic effects increasing and its entactogenic effects decreasing with dosage. 2C-B is the most well-known compound in the 2C family, their general structure being discovered as a result of modifying the structure of mescaline. It is also the most widely used synthetic phenethylamine psychedelic.
MDMA 3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor Psychedelic drug, psychedelic properties. In studies, it has been used ...
("ecstasy") is sometimes said to also have weak psychedelic effects, but it acts and is classified mainly as an
entactogen Entactogens, also known as empathogens or connectogens, are a class of psychoactive drugs that induce the production of experiences of emotional communion, oneness, connectedness, emotional openness—that is, empathy—as particularly observe ...
rather than as a hallucinogen. Certain related drugs like MDA and MMDA have greater psychedelic effects however.


Uses


Recreational

Recreational use of psychedelics has been common since the psychedelic era of the mid-1960s and continues to play a role in various festivals and events, including
Burning Man Burning Man is a week-long large-scale desert event focused on "community, art, self-expression, and self-reliance" held annually in the Western United States. The event's name comes from its ceremony on the penultimate night of the event: the ...
. A survey published in 2013 found that 13.4% of American adults had used a psychedelic. A June 2024 report by the
RAND Corporation The RAND Corporation, doing business as RAND, is an American nonprofit global policy think tank, research institute, and public sector consulting firm. RAND engages in research and development (R&D) in several fields and industries. Since the ...
suggests psilocybin mushrooms may be the most prevalent psychedelic drug among adults in the United States. The RAND national survey indicated that 3.1% of U.S. adults reported using psilocybin in the past year. Roughly 12% of respondents acknowledged lifetime use of psilocybin, while a similar percentage reported having used LSD at some point in their lives.
MDMA 3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor Psychedelic drug, psychedelic properties. In studies, it has been used ...
, also known as ecstasy, showed a lower prevalence of use at 7.6%. Notably, less than 1% of U.S. adults reported using any psychedelic drugs within the past month.


Traditional

A number of frequently mentioned or traditional psychedelics such as '' Ayahuasca'' (which contains DMT), San Pedro, Peyote, and Peruvian torch (which all contain
mescaline Mescaline, also known as mescalin or mezcalin, and in chemical terms 3,4,5-trimethoxyphenethylamine, is a natural product, naturally occurring psychedelic drug, psychedelic alkaloid, protoalkaloid of the substituted phenethylamine class, found ...
), Psilocybe mushrooms (which contain psilocin/
psilocybin Psilocybin, also known as 4-phosphoryloxy-''N'',''N''-dimethyltryptamine (4-PO-DMT), is a natural product, naturally occurring tryptamine alkaloid and Investigational New Drug, investigational drug found in more than List of psilocybin mushroom ...
) and '' Tabernanthe iboga'' (which contains the unique psychedelic ibogaine) all have a long and extensive history of spiritual, shamanic and traditional usage by
indigenous peoples There is no generally accepted definition of Indigenous peoples, although in the 21st century the focus has been on self-identification, cultural difference from other groups in a state, a special relationship with their traditional territ ...
in various world regions, particularly in Latin America, but also
Gabon Gabon ( ; ), officially the Gabonese Republic (), is a country on the Atlantic coast of Central Africa, on the equator, bordered by Equatorial Guinea to the northwest, Cameroon to the north, the Republic of the Congo to the east and south, and ...
, Africa in the case of iboga. Different countries and/or regions have come to be associated with traditional or spiritual use of particular psychedelics, such as the ancient and entheogenic use of psilocybe mushrooms by the native Mazatec people of
Oaxaca Oaxaca, officially the Free and Sovereign State of Oaxaca, is one of the 32 states that compose the political divisions of Mexico, Federative Entities of the Mexico, United Mexican States. It is divided into municipalities of Oaxaca, 570 munici ...
, Mexico or the use of the ayahuasca brew in the
Amazon basin The Amazon basin is the part of South America drained by the Amazon River and its tributary, tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries ...
, particularly in Peru for spiritual and physical healing as well as for religious festivals. Peyote has also been used for several thousand years in the Rio Grande Valley in North America by native tribes as an entheogen. In the
Andean The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long and wide (widest between 18°S ...
region of South America, the San Pedro cactus ( ''Trichocereus macrogonus'' var. ''pachanoi'', syn. ''
Echinopsis pachanoi ''Trichocereus macrogonus'' var. ''pachanoi'' (Synonym (taxonomy), synonyms including ''Trichocereus pachanoi'' and ''Echinopsis pachanoi'') is a fast-growing columnar cactus found in the Andes at in altitude. It is one of a number of kinds of ...
'') has a long history of use, possibly as a
traditional medicine Traditional medicine (also known as indigenous medicine or folk medicine) refers to the knowledge, skills, and practices rooted in the cultural beliefs of various societies, especially Indigenous groups, used for maintaining health and treatin ...
. Archaeological studies have found evidence of use going back two thousand years, to Moche culture, Nazca culture, and Chavín culture. Although authorities of the
Roman Catholic The Catholic Church (), also known as the Roman Catholic Church, is the largest Christian church, with 1.27 to 1.41 billion baptized Catholics worldwide as of 2025. It is among the world's oldest and largest international institut ...
church attempted to suppress its use after the Spanish conquest, this failed, as shown by the Christian element in the common name "San Pedro cactus" –
Saint Peter Saint Peter (born Shimon Bar Yonah; 1 BC – AD 64/68), also known as Peter the Apostle, Simon Peter, Simeon, Simon, or Cephas, was one of the Twelve Apostles of Jesus and one of the first leaders of the Jewish Christian#Jerusalem ekklēsia, e ...
cactus. The name has its origin in the belief that just as St Peter holds the keys to heaven, the effects of the cactus allow users "to reach heaven while still on earth." In 2022, the Peruvian Ministry of Culture declared the traditional use of San Pedro cactus in northern Peru as
cultural heritage Cultural heritage is the heritage of tangible and intangible heritage assets of a group or society that is inherited from past generations. Not all heritages of past generations are "heritage"; rather, heritage is a product of selection by socie ...
. Although people of
Western culture Western culture, also known as Western civilization, European civilization, Occidental culture, Western society, or simply the West, refers to the Cultural heritage, internally diverse culture of the Western world. The term "Western" encompas ...
have tended to use psychedelics for either psychotherapeutic or recreational reasons, most indigenous cultures, particularly in South America, have seemingly tended to use psychedelics for more
supernatural Supernatural phenomena or entities are those beyond the Scientific law, laws of nature. The term is derived from Medieval Latin , from Latin 'above, beyond, outside of' + 'nature'. Although the corollary term "nature" has had multiple meanin ...
reasons such as
divination Divination () is the attempt to gain insight into a question or situation by way of an occultic ritual or practice. Using various methods throughout history, diviners ascertain their interpretations of how a should proceed by reading signs, ...
. This can often be related to "healing" or health as well but typically in the context of finding out what is wrong with the individual, such as using psychedelic states to "identify" a disease and/or its cause, locate lost objects, and identify a victim or even perpetrator of sorcery. In some cultures and regions, even psychedelics themselves, such as ayahuasca and the psychedelic
lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...
of eastern Ecuador ('' Dictyonema huaorani'') that supposedly contains both 5-MeO-DMT and psilocybin, have also been used by witches and sorcerers to conduct their malicious magic, similarly to
nightshade Solanaceae (), commonly known as the nightshades, is a family of flowering plants in the order Solanales. It contains approximately 2,700 species, several of which are used as agricultural crops, medicinal plants, and ornamental plants. Many me ...
deliriants like '' brugmansia'' and '' latua''.


Medical

Psychedelic therapy (or psychedelic-assisted therapy) is the proposed use of psychedelic drugs to treat
mental disorder A mental disorder, also referred to as a mental illness, a mental health condition, or a psychiatric disability, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. A mental disorder is ...
s. As of 2021, psychedelic drugs are controlled substances in most countries and psychedelic therapy is not legally available outside clinical trials, with some exceptions. The procedure for psychedelic therapy differs from that of therapies using conventional
psychiatric medication A psychiatric or psychotropic medication is a psychoactive drug taken to exert an effect on the chemical makeup of the brain and nervous system. Thus, these medications are used to treat mental illnesses. These medications are typically made of ...
s. While conventional medications are usually taken without supervision at least once daily, in contemporary psychedelic therapy the drug is administered in a single session (or sometimes up to three sessions) in a therapeutic context. The therapeutic team prepares the patient for the experience beforehand and helps them integrate insights from the drug experience afterwards. After ingesting the drug, the patient normally wears eyeshades and listens to music to facilitate focus on the psychedelic experience, with the therapeutic team interrupting only to provide reassurance if adverse effects such as anxiety or disorientation arise. As of 2022, the body of high-quality evidence on psychedelic therapy remains relatively small and more, larger studies are needed to reliably show the effectiveness and safety of psychedelic therapy's various forms and applications. On the basis of favorable early results, ongoing research is examining proposed psychedelic therapies for conditions including
major depressive disorder Major depressive disorder (MDD), also known as clinical depression, is a mental disorder characterized by at least two weeks of pervasive depression (mood), low mood, low self-esteem, and anhedonia, loss of interest or pleasure in normally ...
, and
anxiety Anxiety is an emotion characterised by an unpleasant state of inner wikt:turmoil, turmoil and includes feelings of dread over Anticipation, anticipated events. Anxiety is different from fear in that fear is defined as the emotional response ...
and depression linked to
terminal illness Terminal illness or end-stage disease is a disease that cannot be cured or adequately treated and is expected to result in the death of the patient. This term is more commonly used for progressive diseases such as cancer, rather than fatal injur ...
. The United States
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...
has granted breakthrough therapy status, which expedites the assessment of promising drug therapies for potential approval, to psilocybin therapy for treatment-resistant depression and major depressive disorder. It has been proposed that psychedelics used for therapeutic purposes may act as active "super
placebo A placebo ( ) can be roughly defined as a sham medical treatment. Common placebos include inert tablets (like sugar pills), inert injections (like saline), sham surgery, and other procedures. Placebos are used in randomized clinical trials ...
s".


Microdosing

Psychedelic microdosing is the practice of using sub-threshold doses ( microdoses) of psychedelics in an attempt to improve creativity, boost physical energy level, emotional balance, increase performance on problems-solving tasks and to treat anxiety, depression and addiction. The practice of microdosing has become more widespread in the 21st century with more people claiming long-term benefits from the practice. A 2022 study recognized signatures of psilocybin microdosing in
natural language A natural language or ordinary language is a language that occurs naturally in a human community by a process of use, repetition, and change. It can take different forms, typically either a spoken language or a sign language. Natural languages ...
and concluded that low amount of psychedelics have potential for application, and ecological observation of microdosing schedules.


Dosage

The table below provides doses of major serotonergic psychedelics as well as the
entactogen Entactogens, also known as empathogens or connectogens, are a class of psychoactive drugs that induce the production of experiences of emotional communion, oneness, connectedness, emotional openness—that is, empathy—as particularly observe ...
and mild psychedelic
MDMA 3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor Psychedelic drug, psychedelic properties. In studies, it has been used ...
("ecstasy") that have been determined on the basis of
clinical studies Clinical trials are prospective biomedical or behavioral research studies on human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, dietar ...
. Other dosage schemes have also been reported. In the case of dried psilocybin-containing mushrooms, microdoses are 0.1g to 0.3g and psychedelic doses are 1.0g to 3.5–5.0g. The preceding 1.0 to 5.0g range corresponds to psilocybin doses of about 10 to 50mg. Psilocybin-containing mushrooms vary in their psilocybin and psilocin content, but are typically around 1% of the dried weight of the mushrooms (in terms of total or combined psilocybin and psilocin content). Psilocybin and psilocin are similar in potency and dose but psilocin is about 1.4-fold more active, this being related to the difference in
molecular weight A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...
between the two compounds. Some psychedelics, such as 2C-B, 2C-E, and 4-HO-DiPT, have been said to have steep dose–response curves, meaning that the difference in dose between a light experience and an overwhelming disconnection from reality can be small.


Effects


Psychedelic effects

Although several attempts have been made, starting in the 19th and 20th centuries, to define common phenomenological structures of the effects produced by classic psychedelics, a universally accepted taxonomy does not yet exist. At lower doses, features of psychedelic experiences include sensory alterations, such as the warping of surfaces, shape suggestibility,
pareidolia Pareidolia (; ) is the tendency for perception to impose a meaningful interpretation on a nebulous stimulus (physiology), stimulus, usually visual, so that one detects an object, pattern, or meaning where there is none. Pareidolia is a specific bu ...
, and color variations. Users often report intense colors that they have not previously experienced, and repetitive geometric shapes or form constants are common as well. Higher doses often cause intense and fundamental alterations of sensory (notably
visual The visual system is the physiological basis of visual perception (the ability to detect and process light). The system detects, transduces and interprets information concerning light within the visible range to construct an image and buil ...
) perception, such as
synesthesia Synesthesia (American English) or synaesthesia (British English) is a perceptual phenomenon in which stimulation of one sensory or cognitive pathway leads to involuntary experiences in a second sensory or cognitive pathway. People with sy ...
or the experience of additional spatial or temporal dimensions. Tryptamines are well documented to cause classic psychedelic states, such as increased
empathy Empathy is generally described as the ability to take on another person's perspective, to understand, feel, and possibly share and respond to their experience. There are more (sometimes conflicting) definitions of empathy that include but are ...
, visual distortions (drifting, morphing, breathing, melting of various surfaces and objects), auditory hallucinations, ego dissolution or
ego death Ego death is a "complete loss of subjective self-identity". The term is used in various intertwined contexts, with related meanings. The 19th-century philosopher and psychologist William James uses the synonymous term "self-surrender", and Jung ...
with high enough dose, mystical, transpersonal and spiritual experiences, autonomous "
entity An entity is something that Existence, exists as itself. It does not need to be of material existence. In particular, abstractions and legal fictions are usually regarded as entities. In general, there is also no presumption that an entity is Lif ...
" encounters, time distortion, closed eye hallucinations and complete detachment from reality with a high enough dose. Luis Luna describes psychedelic experiences as having a distinctly
gnosis Gnosis is the common Greek noun for knowledge ( γνῶσις, ''gnōsis'', f.). The term was used among various Hellenistic religions and philosophies in the Greco-Roman world. It is best known for its implication within Gnosticism, where ...
-like quality, and says that they offer "learning experiences that elevate consciousness and can make a profound contribution to
personal development Personal development or self-improvement consists of activities that develops a person's capabilities and potential, enhance quality of life, and facilitate the realization of dreams and aspirations. Personal development may take place over the ...
." Czech psychiatrist Stanislav Grof studied the effects of psychedelics like LSD early in his career and said of the experience, that it commonly includes "complex revelatory insights into the nature of existence… typically accompanied by a sense of certainty that this knowledge is ultimately more relevant and 'real' than the perceptions and beliefs we share in everyday life." Traditionally, the standard model for the subjective phenomenological effects of psychedelics has typically been based on LSD, with anything that is considered "psychedelic" evidently being compared to it and its specific effects. Good trips are reportedly deeply pleasurable, and typically involve intense joy or euphoria, a greater appreciation for life, reduced anxiety, a sense of spiritual enlightenment, and a sense of belonging or interconnectedness with the universe. Negative experiences, colloquially known as "bad trips," evoke an array of dark emotions, such as irrational fear, anxiety, panic, paranoia, dread, distrustfulness, hopelessness, and even suicidal ideation. While it is impossible to predict when a bad trip will occur, one's mood, surroundings, sleep, hydration, social setting, and other factors can be controlled (colloquially referred to as " set and setting") to minimize the risk of a bad trip. The concept of "set and setting" also generally appears to be more applicable to psychedelics than to other types of hallucinogens such as deliriants, hypnotics and dissociative anesthetics. Psychedelics include
naturally occurring A natural product is a natural compound or substance produced by a living organism—that is, found in nature. In the broadest sense, natural products include any substance produced by life. Natural products can also be prepared by chemical ...
tryptamines like
psilocybin Psilocybin, also known as 4-phosphoryloxy-''N'',''N''-dimethyltryptamine (4-PO-DMT), is a natural product, naturally occurring tryptamine alkaloid and Investigational New Drug, investigational drug found in more than List of psilocybin mushroom ...
and DMT, the naturally occurring phenethylamine
mescaline Mescaline, also known as mescalin or mezcalin, and in chemical terms 3,4,5-trimethoxyphenethylamine, is a natural product, naturally occurring psychedelic drug, psychedelic alkaloid, protoalkaloid of the substituted phenethylamine class, found ...
, and naturally occurring lysergamides like ergine (lysergic acid amide; LSA), as well as synthetic analogues and
derivative In mathematics, the derivative is a fundamental tool that quantifies the sensitivity to change of a function's output with respect to its input. The derivative of a function of a single variable at a chosen input value, when it exists, is t ...
s like LSD and 2C-B. Many of these psychedelics cause remarkably similar effects, despite their different
chemical structure A chemical structure of a molecule is a spatial arrangement of its atoms and their chemical bonds. Its determination includes a chemist's specifying the molecular geometry and, when feasible and necessary, the electronic structure of the target m ...
s. However, many users anecdotally report that the three major families have subjectively different qualities in the "feel" of the experience, which are difficult to describe. There can also be very substantial differences between the drugs; for instance, 5-MeO-DMT rarely produces the visual effects typical of other psychedelics. As additional examples, DiPT is said to primarily affect the auditory sense, 2C-T-17 and ASR-3001 (5-MeO-iPALT) are said to produce psychedelic effects on thinking or "head space" with few or no visuals, and ''N''-methyltryptamine (NMT) has been said to be a primarily spatial psychedelic. The visuals of psychedelics have been reproduced in video and image form using
artificial intelligence Artificial intelligence (AI) is the capability of computer, computational systems to perform tasks typically associated with human intelligence, such as learning, reasoning, problem-solving, perception, and decision-making. It is a field of re ...
. Some rare individuals do not experience hallucinogenic effects with serotonergic psychedelics.


Other psychoactive effects

Some psychedelics have been associated with other psychoactive effects in addition to their hallucinogenic effects. For example, psychedelics like LSD and DOM have been described as having mild
stimulant Stimulants (also known as central nervous system stimulants, or psychostimulants, or colloquially as uppers) are a class of drugs that increase alertness. They are used for various purposes, such as enhancing attention, motivation, cognition, ...
and/or " psychic-energizing" (i.e., acute
antidepressant Antidepressants are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction. Common side effects of antidepressants include Xerostomia, dry mouth, weight gain, dizziness, headaches, akathi ...
) effects. Some psychedelics and related drugs, like DOET (low doses), Ariadne, and ASR-2001 (2CB-5PrO), have been investigated specifically for such effects. 2C-B has been said to have mild
entactogen Entactogens, also known as empathogens or connectogens, are a class of psychoactive drugs that induce the production of experiences of emotional communion, oneness, connectedness, emotional openness—that is, empathy—as particularly observe ...
ic effects at low doses. Some drugs, such as MDxx compounds like
MDMA 3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor Psychedelic drug, psychedelic properties. In studies, it has been used ...
and MDA as well as α-alkyltryptamines like α-methyltryptamine (AMT), are entactogens and/or stimulants acting at monoamine transporters in addition to having varying degrees of psychedelic effects.


Psychedelic afterglows

Psychedelics are associated with an afterglow, also known as positive subacute or post-experience effects, which may last days or even weeks after the psychedelic experience. These effects include reduction in
psychopathology Psychopathology is the study of mental illness. It includes the signs and symptoms of all mental disorders. The field includes Abnormal psychology, abnormal cognition, maladaptive behavior, and experiences which differ according to social norms ...
and increased
well-being Well-being is what is Intrinsic value (ethics), ultimately good for a person. Also called "welfare" and "quality of life", it is a measure of how well life is going for someone. It is a central goal of many individual and societal endeavors. ...
, mood,
mindfulness Mindfulness is the cognitive skill, usually developed through exercises, of sustaining metacognitive awareness towards the contents of one's own mind and bodily sensations in the present moment. The term ''mindfulness'' derives from the Pali ...
, social functioning,
spirituality The meaning of ''spirituality'' has developed and expanded over time, and various meanings can be found alongside each other. Traditionally, spirituality referred to a religious process of re-formation which "aims to recover the original shape o ...
, and
executive function In cognitive science and neuropsychology, executive functions (collectively referred to as executive function and cognitive control) are a set of cognitive processes that support goal-directed behavior, by regulating thoughts and actions thro ...
ing, and positive behavioral changes. They also include mixed changes in
personality Personality is any person's collection of interrelated behavioral, cognitive, and emotional patterns that comprise a person’s unique adjustment to life. These interrelated patterns are relatively stable, but can change over long time per ...
,
values In ethics and social sciences, value denotes the degree of importance of some thing or action, with the aim of determining which actions are best to do or what way is best to live ( normative ethics), or to describe the significance of different a ...
,
attitude Attitude or Attitude may refer to: Philosophy and psychology * Attitude (psychology), a disposition or state of mind ** Attitude change * Propositional attitude, a mental state held towards a proposition Science and technology * Orientation ...
s,
creativity Creativity is the ability to form novel and valuable Idea, ideas or works using one's imagination. Products of creativity may be intangible (e.g. an idea, scientific theory, Literature, literary work, musical composition, or joke), or a physica ...
, and
flexibility Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations The stiffness, k, of a ...
, as well as
adverse effect An adverse effect is an undesired harmful effect resulting from a medication or other intervention, such as surgery. An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. The term compli ...
s like
headache A headache, also known as cephalalgia, is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of Depression (mood), depression in those with severe ...
s, sleep disturbances, and sometimes increased
psychological distress Mental distress or psychological distress encompasses the symptoms and experiences of a person's internal life that are commonly held to be troubling, confusing or out of the ordinary. Mental distress can potentially lead to a change of behavior, ...
. The afterglow period has been associated with changes in
brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...
function,
neuroplasticity Neuroplasticity, also known as neural plasticity or just plasticity, is the ability of neural networks in the brain to change through neurogenesis, growth and reorganization. Neuroplasticity refers to the brain's ability to reorganize and rewir ...
, and
immune system The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...
function. Both
psychological Psychology is the scientific study of mind and behavior. Its subject matter includes the behavior of humans and nonhumans, both consciousness, conscious and Unconscious mind, unconscious phenomena, and mental processes such as thoughts, feel ...
and
pharmacological Pharmacology is the science of drugs and medications, including a substance's origin, composition, pharmacokinetics, pharmacodynamics, therapeutic use, and toxicology. More specifically, it is the study of the interactions that occur between ...
effects may be involved in the afterglow phenomenon. In 1898, the English writer and intellectual
Havelock Ellis Henry Havelock Ellis (2 February 1859 – 8 July 1939) was an English physician, eugenicist, writer, Progressivism, progressive intellectual and social reformer who studied human sexuality. He co-wrote the first medical textbook in English on h ...
reported a heightened perceptual sensitivity to "the more delicate phenomena of light and shade and color" for a prolonged period of time after his exposure to mescaline. The term "psychedelic afterglow" was first formally coined in the 1960s. Albert Hofmann, the discoverer of LSD, said the following about the aftermath of his first full LSD experience in his 1980 book ''LSD: My Problem Child'': During a speech on his 100th birthday in 2006, Hofmann additionally said of LSD:


Adverse effects

Despite the contrary perception of much of the public, psychedelic drugs are not addictive and are physiologically safe. Risks do exist during an unsupervised psychedelic experience, however; Ira Byock wrote in 2018 in the '' Journal of Palliative Medicine'' that psilocybin is safe when administered to a properly screened patient and supervised by a qualified professional with appropriate set and setting. However, he called for an "abundance of caution" because in the absence of these conditions a range of negative reactions is possible, including "fear, a prolonged sense of dread, or full panic." He notes that driving or even walking in public can be dangerous during a psychedelic experience because of impaired hand-eye coordination and fine motor control. In some cases, individuals taking psychedelics have performed dangerous or fatal acts because they believed they possessed superhuman powers. Psilocybin-induced states of mind share features with states experienced in
psychosis In psychopathology, psychosis is a condition in which a person is unable to distinguish, in their experience of life, between what is and is not real. Examples of psychotic symptoms are delusions, hallucinations, and disorganized or inco ...
, and while a causal relationship between psilocybin and the onset of psychosis has not been established as of 2011, researchers have called for investigation of the relationship. Many of the persistent negative perceptions of psychological risks are unsupported by the currently available scientific evidence, with the majority of reported adverse effects not being observed in a regulated and/or medical context. A population study on associations between psychedelic use and mental illness published in 2013 found no evidence that psychedelic use was associated with increased prevalence of any mental illness. In any case, induction of psychosis has been associated with psychedelics in small percentages of individuals, and the rates appear to be higher in people with
schizophrenia Schizophrenia () is a mental disorder characterized variously by hallucinations (typically, Auditory hallucination#Schizophrenia, hearing voices), delusions, thought disorder, disorganized thinking and behavior, and Reduced affect display, f ...
. Using psychedelics poses certain risks of re-experiencing of the drug's effects, including flashbacks and
hallucinogen persisting perception disorder Hallucinogen persisting perception disorder (HPPD) is a non-psychotic disorder in which a person experiences apparent lasting or persistent visual hallucinations or perceptual distortions after using drugs, including but not limited to psychedeli ...
(HPPD). These non-psychotic effects are poorly studied, but the permanent symptoms (also called "endless trip") are considered to be rare. Serotonergic psychedelics are
agonist An agonist is a chemical that activates a Receptor (biochemistry), receptor to produce a biological response. Receptors are Cell (biology), cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an R ...
s not only of the
serotonin Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...
5-HT2A receptor but also of the serotonin 5-HT2B receptor and other serotonin receptors. A potential risk of frequent repeated use of serotonergic psychedelics is cardiac fibrosis and valvulopathy caused by serotonin 5-HT2B receptor activation. However, single high doses or widely spaced doses (e.g., months) are widely thought to be safe and concerns about cardiac toxicity apply more to chronic psychedelic microdosing or very frequent use (e.g., weekly). Selective serotonin 5-HT2A receptor agonists that do not activate the serotonin 5-HT2B receptor or other serotonin receptors, such as
25CN-NBOH 25CN-NBOH, also known as NBOH-2C-CN, is a compound indirectly derived from the phenethylamine series of hallucinogens, which was discovered in 2014 at the University of Copenhagen. It is a member of the NBOMe family of psychedelic drug, psychedel ...
, DMBMPP, and LPH-5, have been developed and are being studied. Selective serotonin 5-HT2A receptor agonists are expected to avoid the cardiac risks of serotonin 5-HT2B receptor activation.


Overdose

There have been a handful of cases of fatal
overdose A drug overdose (overdose or OD) is the ingestion or application of a drug or other substance in quantities much greater than are recommended. Retrieved on September 20, 2014.
with LSD,
psilocybin Psilocybin, also known as 4-phosphoryloxy-''N'',''N''-dimethyltryptamine (4-PO-DMT), is a natural product, naturally occurring tryptamine alkaloid and Investigational New Drug, investigational drug found in more than List of psilocybin mushroom ...
, and
mescaline Mescaline, also known as mescalin or mezcalin, and in chemical terms 3,4,5-trimethoxyphenethylamine, is a natural product, naturally occurring psychedelic drug, psychedelic alkaloid, protoalkaloid of the substituted phenethylamine class, found ...
. There have also been cases of death with
dimethyltryptamine Dimethyltryptamine (DMT), also known as ''N'',''N''-dimethyltryptamine (''N'',''N''-DMT), is a Psychedelic drug, serotonergic hallucinogen and Investigational New Drug, investigational drug of the substituted tryptamine, tryptamine family tha ...
(DMT), 5-MeO-DMT, 2C-B, Bromo-DragonFLY,
NBOMe The 25-NB (25''x''-NB''x'') series, or NBOMe series, also known as the ''N''-benzylphenethylamines, is a family of serotonergic psychedelics. They are substituted phenethylamines and were derived from the 2C (psychedelics), 2C family. The most c ...
s like 25I-NBOMe, and other psychedelics. LSD and psilocybin appear to have very wide margins of safety with overdose, whereas mescaline and 2C-B have much narrower margins, and NBOMes appear to be especially
toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...
and uniquely linked to
serotonin syndrome Serotonin syndrome (SS) is a group of symptoms that may occur with the use of certain Serotonin, serotonergic medications or Recreational drug use, drugs. The symptoms can range from mild to severe, and are potentially fatal. Symptoms in mild c ...
-type symptoms. In terms of extrapolated human lethal doses based on animal studies and human
case report In medicine, a case report is a detailed report of the symptoms, signs, diagnosis, treatment, and follow-up of an individual patient. Case reports may contain a demographic profile of the patient, but usually describe an unusual or novel occurrenc ...
s, lethal doses of psychedelics relative to typical recreational doses are estimated to be 1,000-fold for LSD, 200-fold for psilocybin, 50-fold for oral DMT (as ayahuasca), and 24-fold for mescaline. Estimates for other psychedelics, like 5-MeO-DMT and 2C-B, could not be made.


Interactions

Serotonin 5-HT2A receptor
antagonist An antagonist is a character in a story who is presented as the main enemy or rival of the protagonist and is often depicted as a villain. Numerous drugs act as serotonin 5-HT2A receptor antagonists, for instance
antidepressant Antidepressants are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction. Common side effects of antidepressants include Xerostomia, dry mouth, weight gain, dizziness, headaches, akathi ...
s like trazodone and
mirtazapine Mirtazapine, sold under the brand name Remeron among others, is an atypical antidepressant, atypical tetracyclic antidepressant, and as such is used primarily to treat Depression (mood), depression. Its effects may take up to four weeks but ca ...
,
antipsychotic Antipsychotics, previously known as neuroleptics and major tranquilizers, are a class of Psychiatric medication, psychotropic medication primarily used to manage psychosis (including delusions, hallucinations, paranoia or disordered thought), p ...
s like quetiapine, olanzapine, and
risperidone Risperidone, sold under the brand name Risperdal among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder, as well as aggressive and self-injurious behaviors associated with autism spectrum disorder. It is t ...
, and other agents like ketanserin, pimavanserin, cyproheptadine, and pizotifen. Such drugs are sometimes referred to as " trip killers" due to their ability to prevent or abort the hallucinogenic effects of psychedelics. Besides serotonin 5-HT2A receptor antagonists, non-hallucinogenic serotonin 5-HT2A receptor
partial agonist In pharmacology, partial agonists are drugs that bind to and activate a given Receptor (biochemistry), receptor, but have only partial Intrinsic activity, efficacy at the receptor relative to a full agonist. They may also be considered Ligand (bio ...
s, such as lisuride, may also block the hallucinogenic effects of serotonergic psychedelics. The serotonin 5-HT1A receptor
partial agonist In pharmacology, partial agonists are drugs that bind to and activate a given Receptor (biochemistry), receptor, but have only partial Intrinsic activity, efficacy at the receptor relative to a full agonist. They may also be considered Ligand (bio ...
buspirone Buspirone, sold under the brand name Buspar among others, is an anxiolytic, a medication primarily used to treat anxiety disorders, particularly generalized anxiety disorder (GAD). It is a serotonin 5-HT1A receptor, 5-HT1A receptor partial ag ...
has been found to markedly reduce the hallucinogenic effects of psilocybin in humans. Conversely, the serotonin 5-HT1A receptor antagonist pindolol has been found to potentiate the hallucinogenic effects of DMT by 2- to 3-fold in humans. Serotonin 5-HT1A receptor agonism may modify and self-inhibit the effects of psychedelics that possess this property. A particularly notable example is 5-methoxytryptamine
derivative In mathematics, the derivative is a fundamental tool that quantifies the sensitivity to change of a function's output with respect to its input. The derivative of a function of a single variable at a chosen input value, when it exists, is t ...
s such as 5-MeO-DMT, which are more potent serotonin 5-HT1A receptor agonists than other psychedelics and have qualitatively unique and differing hallucinogenic effects.
Benzodiazepine Benzodiazepines (BZD, BDZ, BZs), colloquially known as "benzos", are a class of central nervous system (CNS) depressant, depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed t ...
s, for example
diazepam Diazepam, sold under the brand name Valium among others, is a medicine of the benzodiazepine family that acts as an anxiolytic. It is used to treat a range of conditions, including anxiety disorder, anxiety, seizures, alcohol withdrawal syndr ...
,
alprazolam Alprazolam, sold under the brand name Xanax among others, is a fast-acting, potent tranquilizer of moderate duration within the triazolobenzodiazepine group of chemicals called benzodiazepines. Alprazolam is most commonly prescribed in the ...
, clonazepam, and
lorazepam Lorazepam, sold under the brand name Ativan, Tavor among others, is a benzodiazepine medication. It is used to treat anxiety (including anxiety disorders), insomnia, severe agitation, active seizures including status epilepticus, alcoh ...
, as well as
alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...
, which act as GABAA receptor positive allosteric modulators, have been limitedly studied in combination with psychedelics and are not currently known to directly interact with them. However, these GABAergic drugs produce effects such as anxiolysis, sedation, and
amnesia Amnesia is a deficit in memory caused by brain damage or brain diseases,Gazzaniga, M., Ivry, R., & Mangun, G. (2009) Cognitive Neuroscience: The biology of the mind. New York: W.W. Norton & Company. but it can also be temporarily caused by t ...
, and in relation to this, may diminish or otherwise oppose the effects of psychedelics. As a result of this, benzodiazepines and alcohol are often used by recreational users as "trip killers" to manage difficult hallucinogenic experiences with psychedelics, for instance experiences with prominent anxiety. The
safety Safety is the state of being protected from harm or other danger. Safety can also refer to the control of recognized hazards in order to achieve an acceptable level of risk. Meanings The word 'safety' entered the English language in the 1 ...
of this strategy is not entirely clear and might have risks. However, benzodiazepines have been used clinically to manage the adverse psychological effects of psychedelics, for instance in clinical studies and in the
emergency department An emergency department (ED), also known as an accident and emergency department (A&E), emergency room (ER), emergency ward (EW) or casualty department, is a medical treatment facility specializing in emergency medicine, the Acute (medicine), ...
. A clinical trial of
psilocybin Psilocybin, also known as 4-phosphoryloxy-''N'',''N''-dimethyltryptamine (4-PO-DMT), is a natural product, naturally occurring tryptamine alkaloid and Investigational New Drug, investigational drug found in more than List of psilocybin mushroom ...
and
midazolam Midazolam, sold under the brand name Versed among others, is a benzodiazepine medication used for anesthesia, premedication before surgical anesthesia, and procedural sedation, and to treat psychomotor agitation, severe agitation. It induces ...
coadministration found that midazolam clouded the effects of psilocybin and impaired memory of the experience. Benzodiazepines might interfere with the therapeutic effects of psychedelics, such as sustained
antidepressant Antidepressants are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction. Common side effects of antidepressants include Xerostomia, dry mouth, weight gain, dizziness, headaches, akathi ...
effects. Some serotonergic psychedelics, for instance
dimethyltryptamine Dimethyltryptamine (DMT), also known as ''N'',''N''-dimethyltryptamine (''N'',''N''-DMT), is a Psychedelic drug, serotonergic hallucinogen and Investigational New Drug, investigational drug of the substituted tryptamine, tryptamine family tha ...
(DMT) and 5-MeO-DMT, are highly susceptible substrates for
monoamine oxidase Monoamine oxidases (MAO) () are a family of enzymes that catalyze the oxidation of monoamines, employing oxygen to clip off their amine group. They are found bound to the outer membrane of mitochondria in most cell types of the body. The fi ...
(MAO), specifically MAO-A, and hence can be greatly potentiated by monoamine oxidase inhibitors (MAOIs). An example of this is ayahuasca, in which plants containing both DMT and
harmala alkaloid Harmala alkaloids are several alkaloids that act as monoamine oxidase inhibitors (MAOIs). These alkaloids are found in the seeds of ''Peganum harmala'' (also known as harmal or Syrian rue), as well as ''Banisteriopsis caapi'' (ayahuasca), leave ...
s acting as MAOIs such as harmine and harmaline are combined. This allows DMT to become orally active and to have a much longer duration of action than usual. The 2C psychedelics, such as 2C-B, 2C-I, and 2C-E, are also substrates of both MAO-A and MAO-B, and may likewise be greatly potentiated by MAOIs. Examples of MAOIs that may potentiate psychedelics behaving as MAO-A and/or MAO-B substrates include
phenelzine Phenelzine, sold under the brand name Nardil among others, is a non-selective and irreversible monoamine oxidase inhibitor (MAOI) of the hydrazine family which is primarily used as an antidepressant and anxiolytic to treat depression and a ...
,
tranylcypromine Tranylcypromine, sold under the brand name Parnate among others, is a monoamine oxidase inhibitor (MAOI). More specifically, tranylcypromine acts as nonselective and irreversible inhibitor of the enzyme monoamine oxidase (MAO). It is used a ...
, isocarboxazid,
moclobemide Moclobemide, sold under the brand names Amira, Aurorix, Clobemix, Depnil and Manerix among others, is a reversible inhibitor of monoamine oxidase A (RIMA) drug primarily used to treat Clinical depression, depression and social anxiety. It is not ...
, and selegiline. Combination of MAO-substrate psychedelics with MAOIs can result in
overdose A drug overdose (overdose or OD) is the ingestion or application of a drug or other substance in quantities much greater than are recommended. Retrieved on September 20, 2014.
and serious
toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacteria, bacterium, or plant, as well as the effect o ...
, including death. Other psychedelics, such as LSD, are not substrates of MAO and are not potentiated by MAOIs. The extent to which psilocin (and by extension
psilocybin Psilocybin, also known as 4-phosphoryloxy-''N'',''N''-dimethyltryptamine (4-PO-DMT), is a natural product, naturally occurring tryptamine alkaloid and Investigational New Drug, investigational drug found in more than List of psilocybin mushroom ...
) is metabolized by MAO, specifically MAO-A, is not fully clear, but has ranged from 4% to 33% in different studies based on
metabolite In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, c ...
excretion Excretion is elimination of metabolic waste, which is an essential process in all organisms. In vertebrates, this is primarily carried out by the lungs, Kidney (vertebrates), kidneys, and skin. This is in contrast with secretion, where the substa ...
. However, circulating levels of the deaminated metabolite of psilocin are far higher than those of free unmetabolized psilocin with psilocybin administration. An early clinical study of psilocybin in combination with short-term tranylcypromine pretreatment found that tranylcypromine marginally potentiated the
peripheral A peripheral device, or simply peripheral, is an auxiliary hardware device that a computer uses to transfer information externally. A peripheral is a hardware component that is accessible to and controlled by a computer but is not a core compo ...
effects of psilocybin, including pressor effects and
mydriasis Mydriasis is the Pupillary dilation, dilation of the pupil, usually having a non-physiological cause, or sometimes a physiological pupillary response. Non-physiological causes of mydriasis include disease, Physical trauma, trauma, or the use of c ...
, but overall did not significantly modify the psychoactive and hallucinogenic effects of the psilocybin, although some of its emotional effects were said to be reduced and some of its perceptual effects were said to be amplified. Some psychedelics are substrates of
cytochrome P450 Cytochromes P450 (P450s or CYPs) are a Protein superfamily, superfamily of enzymes containing heme as a cofactor (biochemistry), cofactor that mostly, but not exclusively, function as monooxygenases. However, they are not omnipresent; for examp ...
(CYP450)
enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...
s, for instance LSD being a substrate of CYP2D6 as well as of several other CYP450 enzymes. As such, CYP450 inhibitors may increase exposure to CYP450-substrate psychedelics such as LSD and thereby potentiate their effects as well as risks. A clinical study found that administration of LSD to people taking paroxetine, a
selective serotonin reuptake inhibitor Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs that are typically used as antidepressants in the treatment of major depressive disorder, anxiety disorders, and other psychological conditions. SSRIs primarily work by blo ...
(SSRI) and strong CYP2D6 inhibitor, increased LSD exposure by about 1.5-fold. The combination was well-tolerated and did not modify the pleasant subjective effects or physiological effects of LSD, whereas negative effects of LSD, including "bad drug effect",
anxiety Anxiety is an emotion characterised by an unpleasant state of inner wikt:turmoil, turmoil and includes feelings of dread over Anticipation, anticipated events. Anxiety is different from fear in that fear is defined as the emotional response ...
, and
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. It can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the throat. Over 30 d ...
, were reduced. Similarly to the findings with a strong CYP2D6 inhibitor, a pharmacogenomic clinical study with LSD found that LSD levels were 75% higher in people with non-functional CYP2D6 ( poor metabolizers) compared to those with functional CYP2D6.
Serotonin syndrome Serotonin syndrome (SS) is a group of symptoms that may occur with the use of certain Serotonin, serotonergic medications or Recreational drug use, drugs. The symptoms can range from mild to severe, and are potentially fatal. Symptoms in mild c ...
can be caused by combining psychedelics with other serotonergic drugs, including certain
antidepressant Antidepressants are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction. Common side effects of antidepressants include Xerostomia, dry mouth, weight gain, dizziness, headaches, akathi ...
s,
opioid Opioids are a class of Drug, drugs that derive from, or mimic, natural substances found in the Papaver somniferum, opium poppy plant. Opioids work on opioid receptors in the brain and other organs to produce a variety of morphine-like effects, ...
s, psychostimulants (e.g.
MDMA 3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor Psychedelic drug, psychedelic properties. In studies, it has been used ...
),
serotonin Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...
5-HT1 agonists (e.g.
triptan Triptans are a family of tryptamine-based medication, drugs used as abortive medication in the treatment of migraines and cluster headaches. This drug class was first commercially introduced in the 1990s. While effective at treating individual h ...
s),
herb Herbs are a widely distributed and widespread group of plants, excluding vegetables, with savory or aromatic properties that are used for flavoring and garnishing food, for medicinal purposes, or for fragrances. Culinary use typically distingu ...
s or supplements, and others. A high rate of
seizure A seizure is a sudden, brief disruption of brain activity caused by abnormal, excessive, or synchronous neuronal firing. Depending on the regions of the brain involved, seizures can lead to changes in movement, sensation, behavior, awareness, o ...
s has been reported when people on
lithium Lithium (from , , ) is a chemical element; it has chemical symbol, symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard temperature and pressure, standard conditions, it is the least dense metal and the ...
have taken serotonergic psychedelics. In an analysis of online reports, 47% of 62accounts reported seizures when a psychedelic was taken while on lithium. The mechanism underlying this apparent interaction is unclear.


Pharmacology


Mechanism of action

Most serotonergic psychedelics act as non-selective
agonist An agonist is a chemical that activates a Receptor (biochemistry), receptor to produce a biological response. Receptors are Cell (biology), cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an R ...
s of serotonin receptors, including of the
serotonin Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...
5-HT2 receptors, but often also of other serotonin receptors, such as the serotonin 5-HT1 receptors. They are thought to mediate their hallucinogenic effects specifically by activation of serotonin 5-HT2A receptors. Psychedelics (including tryptamines like psilocin, DMT, and 5-MeO-DMT; phenethylamines like
mescaline Mescaline, also known as mescalin or mezcalin, and in chemical terms 3,4,5-trimethoxyphenethylamine, is a natural product, naturally occurring psychedelic drug, psychedelic alkaloid, protoalkaloid of the substituted phenethylamine class, found ...
, DOM, and 2C-B; and ergolines and lysergamides like LSD) all act as agonists of the serotonin 5-HT2A receptors. Some psychedelics, such as phenethylamines like DOM and 2C-B, show high selectivity for the serotonin 5-HT2 receptors over other serotonin receptors. There is a very strong correlation between 5-HT2A receptor
affinity Affinity may refer to: Commerce, finance and law * Affinity (law), kinship by marriage * Affinity analysis, a market research and business management technique * Affinity Credit Union, a Saskatchewan-based credit union * Affinity Equity Pa ...
and human hallucinogenic potency. In addition, the intensity of hallucinogenic effects in humans is directly correlated with the level of serotonin 5-HT2A receptor occupancy as measured with
positron emission tomography Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, r ...
(PET)
imaging Imaging is the representation or reproduction of an object's form; especially a visual representation (i.e., the formation of an image). Imaging technology is the application of materials and methods to create, preserve, or duplicate images. ...
. Serotonin 5-HT2A receptor blockade with drugs like the semi-selective ketanserin and the non-selective
risperidone Risperidone, sold under the brand name Risperdal among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder, as well as aggressive and self-injurious behaviors associated with autism spectrum disorder. It is t ...
can abolish the hallucinogenic effects of psychedelics in humans. However, studies with more selective serotonin 5-HT2A receptor antagonists, like pimavanserin, are still needed. In animals, potency for stimulus generalization to the psychedelic DOM in drug discrimination tests is strongly correlated with serotonin 5-HT2A receptor affinity. Non-selective serotonin 5-HT2A receptor antagonists, like ketanserin and pirenperone, and selective serotonin 5-HT2A receptor antagonists, like volinanserin (MDL-100907), abolish the stimulus generalization of psychedelics in drug discrimination tests. Conversely, serotonin 5-HT2B and 5-HT2C receptor antagonists are ineffective. The potencies of serotonin 5-HT2 receptor antagonists in blocking psychedelic substitution are strongly correlated with their serotonin 5-HT2A receptor affinities. Highly selective serotonin 5-HT2A receptor agonists have recently been developed and show stimulus generalization to psychedelics, whereas selective serotonin 5-HT2C receptor agonists do not do so. The head-twitch response (HTR) is induced by serotonergic psychedelics and is a behavioral proxy of psychedelic-like effects in animals. The HTR is invariably induced by serotonergic psychedelics, is blocked by selective serotonin 5-HT2A receptor antagonists, and is abolished in serotonin 5-HT2A receptor
knockout mice A knockout mouse, or knock-out mouse, is a genetically modified mouse (''Mus musculus'') in which researchers have inactivated, or " knocked out", an existing gene by replacing it or disrupting it with an artificial piece of DNA. They are importan ...
. In addition, there is a strong correlation between hallucinogenic potency in humans and potency in the HTR assay. Moreover, the HTR paradigm is one of the only animal tests that can distinguish between hallucinogenic serotonin 5-HT2A receptor agonists and non-hallucinogenic serotonin 5-HT2A receptor agonists, such as lisuride. In accordance with the preceding animal and human findings, it has been said that the evidence that the serotonin 5-HT2A receptor mediates the hallucinogenic effects of serotonergic psychedelics is overwhelming. The serotonin 5-HT2A receptor activates several downstream
signaling pathway In biology, cell signaling (cell signalling in British English) is the process by which a cell interacts with itself, other cells, and the environment. Cell signaling is a fundamental property of all cellular life in both prokaryotes and eukary ...
s. These include the Gq, β-arrestin2, and other pathways. Activation of both the Gq and β-arrestin2 pathways have been implicated in mediating the hallucinogenic effects of serotonergic psychedelics. However, subsequently, activation of the Gq pathway and not β-arrestin2 has been implicated. Interestingly, Gq signaling appeared to mediate hallucinogenic-like effects, whereas β-arrestin2 mediated receptor downregulation and tachyphylaxis. The lack of psychedelic effects with non-hallucinogenic serotonin 5-HT2A receptor agonists may be due to partial agonism of the serotonin 5-HT2A receptor with
efficacy Efficacy is the ability to perform a task to a satisfactory or expected degree. The word comes from the same roots as '' effectiveness'', and it has often been used synonymously, although in pharmacology a distinction is now often made betwee ...
insufficient to produce psychedelic effects or may be due to biased agonism of the serotonin 5-HT2A receptor. There appears to be a threshold level of Gq activation (in terms of intrinsic activity, with >70%) required for production of hallucinogenic effects. Full agonists and
partial agonist In pharmacology, partial agonists are drugs that bind to and activate a given Receptor (biochemistry), receptor, but have only partial Intrinsic activity, efficacy at the receptor relative to a full agonist. They may also be considered Ligand (bio ...
s above this threshold are psychedelic 5-HT2A receptor agonists, whereas partial agonists below this threshold, such as lisuride, 2-bromo-LSD, 6-fluoro-DET, 6-MeO-DMT, and Ariadne, are non-hallucinogenic 5-HT2A receptor agonists. In addition, biased agonists that activate β-arrestin2 signaling but not Gq signaling, such as ITI-1549, IHCH-7086, and 25N-N1-Nap, are non-hallucinogenic serotonin 5-HT2A receptor agonists. The hallucinogenic effects of serotonergic psychedelics may be critically mediated by serotonin 5-HT2A receptor activation in the medial prefrontal cortex (mPFC). Layer V pyramidal neurons in this area are especially discussed. Activation of serotonin 5-HT2A receptors in the mPFC results in marked excitatory and inhibitory effects as well as increased release of
glutamate Glutamic acid (symbol Glu or E; known as glutamate in its anionic form) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a Essential amino acid, non-essential nutrient for humans, meaning that ...
and
GABA GABA (gamma-aminobutyric acid, γ-aminobutyric acid) is the chief inhibitory neurotransmitter in the developmentally mature mammalian central nervous system. Its principal role is reducing neuronal excitability throughout the nervous system. GA ...
. Direct injection of serotonin 5-HT2A receptor agonists into the mPFC produces the HTR. Drugs that suppress glutamatergic activity in the mPFC, including
AMPA receptor The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA receptor, AMPAR, or quisqualate receptor) is an ionotropic receptor, ionotropic glutamate receptor (iGluR) and predominantly sodium ion channel that mediates fast excitator ...
antagonists, metabotropic glutamate mGlu2/ 3 receptor agonists, μ-opioid receptor agonists, and
adenosine Adenosine (symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9- glycosidic bond. Adenosine is one of the four nucleoside build ...
A1 receptor agonists, block or suppress many of the neurochemical and behavioral effects of serotonergic psychedelics, including the HTR. Metabotropic glutamate mGlu2 receptors are primarily expressed as presynaptic autoreceptors and have inhibitory effects on glutamate release. Serotonergic psychedelics have been found to produce
frontal cortex The frontal lobe is the largest of the four major lobes of the brain in mammals, and is located at the front of each cerebral hemisphere (in front of the parietal lobe and the temporal lobe). It is parted from the parietal lobe by a groove betw ...
hyperactivity Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by symptoms of inattention, hyperactivity, impulsivity, and emotional dysregulation that are excessive and pervasive, impairing in multiple ...
in humans in PET and
single-photon emission computed tomography Single-photon emission computed tomography (SPECT, or less commonly, SPET) is a nuclear medicine tomography, tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera ...
(SPECT) imaging studies. The PFC projects to many other cortical and subcortical brain areas, such as the locus coeruleus,
nucleus accumbens The nucleus accumbens (NAc or NAcc; also known as the accumbens nucleus, or formerly as the ''nucleus accumbens septi'', Latin for ' nucleus adjacent to the septum') is a region in the basal forebrain rostral to the preoptic area of the hypo ...
, and
amygdala The amygdala (; : amygdalae or amygdalas; also '; Latin from Greek language, Greek, , ', 'almond', 'tonsil') is a paired nucleus (neuroanatomy), nuclear complex present in the Cerebral hemisphere, cerebral hemispheres of vertebrates. It is c ...
, among others, and activation of the PFC by serotonergic psychedelics may thereby indirectly modulate these areas. In addition to the PFC, there is moderate to high expression of serotonin 5-HT2A receptors in the
primary visual cortex The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus ...
(V1), as well as expression of the serotonin 5-HT2A receptor in other visual areas, and activation of these receptors may contribute to or mediate the visual effects of serotonergic psychedelics. Serotonergic psychedelics also directly or indirectly modulate a variety of other brain areas, like the claustrum, and this may be involved in their effects as well. Serotonin, as well as drugs that increase serotonin levels, like the serotonin precursor 5-hydroxytryptophan (5-HTP), serotonin reuptake inhibitors, and serotonin releasing agents, are non-hallucinogenic in humans despite increasing activation of serotonin 5-HT2A receptors. Serotonin is a hydrophilic molecule which cannot easily cross
biological membrane A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates the interior of a cell from the external environment or creates intracellular compartments by serving as a boundary between one part of th ...
s without
active transport In cellular biology, active transport is the movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient. Active transport requires cellula ...
, and the serotonin 5-HT2A receptor is usually expressed as a
cell surface receptor Cell surface receptors (membrane receptors, transmembrane receptors) are receptors that are embedded in the plasma membrane of cells. They act in cell signaling by receiving (binding to) extracellular molecules. They are specialized integra ...
that is readily accessible to extracellular serotonin. The HTR, a behavioral proxy of psychedelic-like effects, appears to be mediated by activation of
intracellular This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions ...
ly expressed serotonin 5-HT2A receptors in a population of mPFC neurons that do not also express the serotonin transporter (SERT) and hence cannot be activated by serotonin. In contrast to serotonin, serotonergic psychedelics are more
lipophilic Lipophilicity (from Greek language, Greek λίπος "fat" and :wikt:φίλος, φίλος "friendly") is the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. Such compounds are c ...
than serotonin and are able to readily enter these neurons and activate the serotonin 5-HT2A receptors within them. Artificial expression of the SERT in this population of neurons in animals resulted in a serotonin releasing agent that doesn't normally produce the HTR being able to do so. Although serotonin itself is non-hallucinogenic, at very high concentrations achieved pharmacologically (e.g., injected into the brain or with massive doses of 5-HTP) it can produce psychedelic-like effects in animals by being metabolized by indolethylamine ''N''-methyltransferase (INMT) into more lipophilic ''N''- methylated tryptamines like ''N''-methylserotonin and bufotenin (''N'',''N''-dimethylserotonin). In addition to their hallucinogenic effects, serotonergic psychedelics may also produce a variety of other effects, including
psychoplastogen Psychoplastogens, also known as neuroplastogens, are a group of Small molecule#Drugs, small molecule drugs that produce rapid and sustained effects on neuronal structure and function, intended to manifest therapeutic benefit after a single admin ...
ic (i.e.,
neuroplasticity Neuroplasticity, also known as neural plasticity or just plasticity, is the ability of neural networks in the brain to change through neurogenesis, growth and reorganization. Neuroplasticity refers to the brain's ability to reorganize and rewir ...
-enhancing),
antidepressant Antidepressants are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction. Common side effects of antidepressants include Xerostomia, dry mouth, weight gain, dizziness, headaches, akathi ...
,
anxiolytic An anxiolytic (; also antipanic or anti-anxiety agent) is a medication or other intervention that reduces anxiety. This effect is in contrast to anxiogenic agents which increase anxiety. Anxiolytic medications are used for the treatment of anxie ...
,
empathy Empathy is generally described as the ability to take on another person's perspective, to understand, feel, and possibly share and respond to their experience. There are more (sometimes conflicting) definitions of empathy that include but are ...
-enhancing or prosocial effects, anti-obsessional, anti-addictive,
anti-inflammatory Anti-inflammatory is the property of a substance or treatment that reduces inflammation, fever or swelling. Anti-inflammatory drugs, also called anti-inflammatories, make up about half of analgesics. These drugs reduce pain by inhibiting mechan ...
and
immunomodulator Immunotherapy or biological therapy is the treatment of disease by activating or suppressing the immune system. Immunotherapies designed to elicit or amplify an immune response are classified as ''activation immunotherapies,'' while immunotherap ...
y effects,
analgesic An analgesic drug, also called simply an analgesic, antalgic, pain reliever, or painkiller, is any member of the group of drugs used for pain management. Analgesics are conceptually distinct from anesthetics, which temporarily reduce, and in s ...
effects, and/or antimigraine effects. While psychedelics themselves are also being clinically evaluated for these potential therapeutic benefits, non-hallucinogenic serotonin 5-HT2A receptor agonists, which are often analogues of serotonergic psychedelics, have been developed and are being studied for potential use in medicine in an attempt to provide some such benefits without hallucinogenic effects. Although the hallucinogenic effects of serotonergic psychedelics are thought to be mediated by serotonin 5-HT2A receptor activation, interactions with other receptors, such as the serotonin 5-HT1A, 5-HT1B, 5-HT2B, and 5-HT2C receptors among many others, may additionally contribute to and modulate their effects. Interestingly, some psychedelics, such as LSD and psilocybin, have been claimed to act as positive allosteric modulators of the tropomyosin receptor kinase B (TrkB), one of the signaling receptors of
brain-derived neurotrophic factor Brain-derived neurotrophic factor (BDNF), or abrineurin, is a protein found in the and the periphery. that, in humans, is encoded by the ''BDNF'' gene. BDNF is a member of the neurotrophin family of growth factors, which are related to the can ...
(BDNF). However, this finding has yet to be replicated. Moreover, despite the apparent TrkB potentiation, the psychoplastogenic effects of serotonergic psychedelics, including dendritogenesis, spinogenesis, and synaptogenesis, appear to be mediated by activation of serotonin 5-HT2A receptors, whereas psychedelics do not generally stimulate neurogenesis. The factors responsible for differences in psychoactive and hallucinogenic effects between different psychedelics are incompletely understood but may include (1) differences in selectivity for the serotonin 5-HT2A receptor or
off-target activity Off-target activity is biological activity of a drug that is different from and not at that of its intended biological target. It most commonly contributes to side effects. However, in some cases, off-target activity can be taken advantage of for t ...
; (2) differences in functional selectivity for different serotonin 5-HT2A receptor downstream signaling pathways; and (3) differences in patterns or balances of distribution to different brain areas.


Chemistry

The three major chemical groups of serotonergic psychedelics include the tryptamines, phenethylamines, and lysergamides, which each have different profiles of pharmacological activity.


Tryptamines

Tryptamines are
derivative In mathematics, the derivative is a fundamental tool that quantifies the sensitivity to change of a function's output with respect to its input. The derivative of a function of a single variable at a chosen input value, when it exists, is t ...
s of tryptamine and are structurally related to the monoamine neurotransmitter
serotonin Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...
(also known as 5-hydroxytryptamine or 5-HT). Many tryptamines act as non-selective serotonin receptor agonists, including of the serotonin 5-HT2A receptor. Some tryptamines also act as monoamine releasing agents, including of serotonin, norepinephrine, and/or dopamine. Examples of psychedelic tryptamines include psilocin and
psilocybin Psilocybin, also known as 4-phosphoryloxy-''N'',''N''-dimethyltryptamine (4-PO-DMT), is a natural product, naturally occurring tryptamine alkaloid and Investigational New Drug, investigational drug found in more than List of psilocybin mushroom ...
,
dimethyltryptamine Dimethyltryptamine (DMT), also known as ''N'',''N''-dimethyltryptamine (''N'',''N''-DMT), is a Psychedelic drug, serotonergic hallucinogen and Investigational New Drug, investigational drug of the substituted tryptamine, tryptamine family tha ...
(DMT), 5-MeO-DMT, bufotenin, α-methyltryptamine (αMT), 4-AcO-DMT (psilacetin), 4-HO-MET, 5-MeO-MiPT, and 5-MeO-DiPT, among others.
Harmala alkaloid Harmala alkaloids are several alkaloids that act as monoamine oxidase inhibitors (MAOIs). These alkaloids are found in the seeds of ''Peganum harmala'' (also known as harmal or Syrian rue), as well as ''Banisteriopsis caapi'' (ayahuasca), leave ...
s like harmaline and iboga-type alkaloids like ibogaine are cyclized tryptamines and may also be considered hallucinogenic tryptamines.


Phenethylamines

Phenethylamines, as well as
amphetamine Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...
s (α-methylphenethylamines), are derivatives of β-phenethylamine and are structurally related to the monoamine neurotransmitters
dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...
,
norepinephrine Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic compound, organic chemical in the catecholamine family that functions in the brain and human body, body as a hormone, neurotransmitter and neuromodulator. The ...
, and
epinephrine Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands a ...
. Some phenethylamines and amphetamines, particularly those with
methoxy In organic chemistry, a methoxy group is the functional group consisting of a methyl group bound to oxygen. This alkoxy group has the formula . On a benzene ring, the Hammett equation classifies a methoxy substituent at the ''para'' position a ...
and other substitions on the phenyl ring, are potent serotonin 5-HT2 receptor agonists, including of the serotonin 5-HT2A receptor, and can produce psychedelic effects. In contrast to phenethylamines and amphetamines generally, most psychedelic phenethylamines are not monoamine releasing agents. Examples of psychedelic phenethylamines and amphetamines include
mescaline Mescaline, also known as mescalin or mezcalin, and in chemical terms 3,4,5-trimethoxyphenethylamine, is a natural product, naturally occurring psychedelic drug, psychedelic alkaloid, protoalkaloid of the substituted phenethylamine class, found ...
and other scalines like trimethoxyamphetamine (TMA) and escaline, the 2C drugs like 2C-B, 2C-E, and 2C-I, the DOx drugs like DOB, DOI, and DOM, certain MDxx drugs like MDA and
MDMA 3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor Psychedelic drug, psychedelic properties. In studies, it has been used ...
(weak psychedelics), and the
NBOMe The 25-NB (25''x''-NB''x'') series, or NBOMe series, also known as the ''N''-benzylphenethylamines, is a family of serotonergic psychedelics. They are substituted phenethylamines and were derived from the 2C (psychedelics), 2C family. The most c ...
(25x-NBx) drugs like 25I-NBOMe, among others.


Lysergamides

Lysergamides are ergoline derivatives related to the ergot alkaloids. They are notable in containing both tryptamine and phenethylamine within their
chemical structure A chemical structure of a molecule is a spatial arrangement of its atoms and their chemical bonds. Its determination includes a chemist's specifying the molecular geometry and, when feasible and necessary, the electronic structure of the target m ...
s. As such, ergolines and lysergamides may be considered structurally related to the monoamine neurotransmitters. Many ergolines and lysergamides act as highly promiscuous ligands of monoamine receptors, including of
serotonin Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...
,
dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...
, and adrenergic receptors. Some lysergamides are efficacious serotonin 5-HT2A receptor agonists and thereby produce psychedelic effects. Examples of psychedelic lysergamides include
lysergic acid diethylamide Lysergic acid diethylamide, commonly known as LSD (from German ; often referred to as acid or lucy), is a Semisynthesis, semisynthetic, Hallucinogen, hallucinogenic compound derived from ergot, known for its powerful psychological effects and ...
(LSD), ergine (lysergic acid amide; LSA), isoergine (isolysergic acid amide; iso-LSA), ETH-LAD, AL-LAD, 1P-LSD, 1S-LSD, ALD-52 (1A-LSD), LA-SS-Az (LSZ), ergonovine (ergometrine; lysergic acid propanolamide), methylergometrine (methylergonovine), and methysergide (methylmethylergonovine), among others. Ergine, isoergine, and ergonovine occur naturally in morning glories and certain
fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
like ergot and '' Periglandula'' species, while others like LSD are synthetic. LSD is among the most potent psychedelics, as well as psychoactive drugs in general, that are known.


Others

Other psychedelics not belonging to any of the above three structural families have been discovered, for instance certain arylpiperazine
derivative In mathematics, the derivative is a fundamental tool that quantifies the sensitivity to change of a function's output with respect to its input. The derivative of a function of a single variable at a chosen input value, when it exists, is t ...
s like quipazine, the
antiretroviral drug The management of HIV/AIDS normally includes the use of multiple Antiviral drug, antiretroviral drugs as a strategy to control HIV/AIDS, HIV infection. There are several classes of antiretroviral agents that act on different stages of the HIV li ...
efavirenz, and simplified or partial lysergamides (which are also rigid tryptamines and/or phenethylamines) like NDTDI and DEMPDHPCA.


History


Early history

Psychedelics occurring in
plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...
s,
fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
, and
animal Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...
s have been used by
indigenous people There is no generally accepted definition of Indigenous peoples, although in the 21st century the focus has been on self-identification, cultural difference from other groups in a state, a special relationship with their traditional territ ...
s throughout the world for thousands of years. These psychedelics and their sources include
psilocybin Psilocybin, also known as 4-phosphoryloxy-''N'',''N''-dimethyltryptamine (4-PO-DMT), is a natural product, naturally occurring tryptamine alkaloid and Investigational New Drug, investigational drug found in more than List of psilocybin mushroom ...
and psilocin in psilocybin-containing mushrooms (teonanacatl),
dimethyltryptamine Dimethyltryptamine (DMT), also known as ''N'',''N''-dimethyltryptamine (''N'',''N''-DMT), is a Psychedelic drug, serotonergic hallucinogen and Investigational New Drug, investigational drug of the substituted tryptamine, tryptamine family tha ...
(DMT) in ayahuasca (a combination typically of '' Psychotria viridis'' and '' Banisteriopsis caapi''), bufotenin in '' Anadenanthera'' trees, 5-MeO-DMT in the Colorado River Toad,
mescaline Mescaline, also known as mescalin or mezcalin, and in chemical terms 3,4,5-trimethoxyphenethylamine, is a natural product, naturally occurring psychedelic drug, psychedelic alkaloid, protoalkaloid of the substituted phenethylamine class, found ...
in peyote (peyotl) and San Pedro cacti, and ergine and isoergine in morning glories (ololiuqui, tlitliltzin) and ergot, among others. The kykeon of the
Eleusinian Mysteries The Eleusinian Mysteries () were initiations held every year for the Cult (religious practice), cult of Demeter and Persephone based at the Panhellenic Sanctuary of Eleusis in ancient Greece. They are considered the "most famous of the secret rel ...
in
Ancient Greece Ancient Greece () was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity (), that comprised a loose collection of culturally and linguistically r ...
might have been a psychedelic, for instance ergot or psilocybin-containing mushrooms.Valencic, I. (1994). Has the Mystery of the Eleusinian Mysteries been solved. Yearbook for Ethnomedicine and the Study of Consciousness, 3, 325–336. https://www.druglibrary.org/schaffer/lsd/valencic.htm The earliest archeological evidence of the use of psychedelic plants and fungi by humans dates back roughly 10,000years.


Western characterization

Psychedelics were discovered by the
Western world The Western world, also known as the West, primarily refers to various nations and state (polity), states in Western Europe, Northern America, and Australasia; with some debate as to whether those in Eastern Europe and Latin America also const ...
and the
scientific community The scientific community is a diverse network of interacting scientists. It includes many "working group, sub-communities" working on particular scientific fields, and within particular institutions; interdisciplinary and cross-institutional acti ...
relatively late. The use of hallucinogenic snuffs by indigenous
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
n people was first observed by
Western Western may refer to: Places *Western, Nebraska, a village in the US *Western, New York, a town in the US *Western Creek, Tasmania, a locality in Australia *Western Junction, Tasmania, a locality in Australia *Western world, countries that id ...
explorers like
Christopher Columbus Christopher Columbus (; between 25 August and 31 October 1451 – 20 May 1506) was an Italians, Italian explorer and navigator from the Republic of Genoa who completed Voyages of Christopher Columbus, four Spanish-based voyages across the At ...
as early as 1496. The first written description of an observed psychedelic experience, with cohoba, was published by Ramon Pane in 1511. Spanish explorers observed the use of psilocybin-containing mushrooms (teonanacatl) in
Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
as early as 1519 with the arrival of
Hernán Cortés Hernán Cortés de Monroy y Pizarro Altamirano, 1st Marquis of the Valley of Oaxaca (December 1485 – December 2, 1547) was a Spanish ''conquistador'' who led an expedition that caused the fall of the Aztec Empire and brought large portions o ...
. Spanish ethnographer Bernardino de Sahagún traveled to Mexico in 1529 and described the use of these mushrooms in his books. The
botanist Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...
s Richard Spruce and Alfred Russel Wallace observed and described the use of ayahuasca in the
Amazon Amazon most often refers to: * Amazon River, in South America * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon (company), an American multinational technology company * Amazons, a tribe of female warriors in Greek myth ...
in the 1850s.


The phenethylamine psychedelic mescaline

Mescaline Mescaline, also known as mescalin or mezcalin, and in chemical terms 3,4,5-trimethoxyphenethylamine, is a natural product, naturally occurring psychedelic drug, psychedelic alkaloid, protoalkaloid of the substituted phenethylamine class, found ...
is sometimes described as the "first psychedelic", as it was the first to be discovered and characterized by the Western world. American
physician A physician, medical practitioner (British English), medical doctor, or simply doctor is a health professional who practices medicine, which is concerned with promoting, maintaining or restoring health through the Medical education, study, Med ...
John Raleigh Briggs, living in
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
, learned of peyote from Native Americans and Mexicans, who told him that it produced "beautiful visions" and made them journey into the "spirit world". He obtained mescal buttons from
Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
and published a
journal article An article or piece is a written work published in a print or electronic medium, for the propagation of news, research results, academic analysis or debate. News A news article discusses current or recent news of either general interest (i.e. ...
about trying a very low dose of them in May 1887. This article is said to have brought peyote into North American
pharmacology Pharmacology is the science of drugs and medications, including a substance's origin, composition, pharmacokinetics, pharmacodynamics, therapeutic use, and toxicology. More specifically, it is the study of the interactions that occur betwee ...
. Briggs described the physiological effects of his experience, such as increased heart rate, and of experiencing " intoxication". The article was read by George Davis, of Parke, Davis and Company, who then obtained the buttons from Briggs in June 1887. Parke-Davis attempted to market peyote as a cardiac stimulant and for other uses, but met with little success. The German pharmacologist Louis Lewin obtained mescal buttons from Parke-Davis during a trip to the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
in 1887 and began studying them and sharing his findings. The first known published description of a hallucinogenic peyote experience was by American
neurologist Neurology (from , "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the nervous system, which comprises the brain, the ...
Silas Weir Mitchell in December 1896. After reading Mitchell's article, others, including
psychologist A psychologist is a professional who practices psychology and studies mental states, perceptual, cognitive, emotional, and social processes and behavior. Their work often involves the experimentation, observation, and explanation, interpretatio ...
and sexologist
Havelock Ellis Henry Havelock Ellis (2 February 1859 – 8 July 1939) was an English physician, eugenicist, writer, Progressivism, progressive intellectual and social reformer who studied human sexuality. He co-wrote the first medical textbook in English on h ...
, American psychologist
William James William James (January 11, 1842 – August 26, 1910) was an American philosopher and psychologist. The first educator to offer a psychology course in the United States, he is considered to be one of the leading thinkers of the late 19th c ...
, and German pharmacologist,
chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a graduated scientist trained in the study of chemistry, or an officially enrolled student in the field. Chemists study the composition of ...
, and Lewin rival Arthur Heffter, among others, tried peyote and described their experiences. Heffter isolated and ingested mescaline from peyote, experiencing psychedelic effects with the pure compound, in 1897, and published his findings in 1898. Austrian
chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a graduated scientist trained in the study of chemistry, or an officially enrolled student in the field. Chemists study the composition of ...
Ernst Späth synthesized mescaline for the first time in 1919. The German
pharmaceutical company The pharmaceutical industry is a Medicine, medical industry that discovers, develops, produces, and markets pharmaceutical goods such as medications and medical devices. Medications are then administered to (or Self-medicate, self-administered b ...
Merck then began distributing pharmaceutical mescaline in 1920. The German psychiatrist Kurt Beringer, a student of Lewin and an acquaintance of
Hermann Hesse Hermann Karl Hesse (; 2 July 1877 – 9 August 1962) was a Germans, German-Swiss people, Swiss poet and novelist, and the 1946 Nobel Prize in Literature laureate. His interest in Eastern philosophy, Eastern religious, spiritual, and philosophic ...
and
Carl Jung Carl Gustav Jung ( ; ; 26 July 1875 – 6 June 1961) was a Swiss psychiatrist, psychotherapist, and psychologist who founded the school of analytical psychology. A prolific author of Carl Jung publications, over 20 books, illustrator, and corr ...
, became the father of psychedelic psychiatry and conducted experiments with mescaline in more than 60people starting in 1921. He published his monograph on the subject, '' Der Meskalinrausch'' (''Mescaline Intoxication''), in 1927. German– American psychologist Heinrich Klüver published his monograph, ''Mescal: The Divine Plant and Its Psychological Effects'', in English in 1928. He is said to have been the first to attempt to provide a phenomenological description of the psychedelic experience.


Tryptamine and lysergamide psychedelics

Austrian anthropologist and ethnobotanist Blas Pablo Reko, traveling through Central and
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
, wrote of the use of teonanacatl by native Mexican people in
Oaxaca Oaxaca, officially the Free and Sovereign State of Oaxaca, is one of the 32 states that compose the political divisions of Mexico, Federative Entities of the Mexico, United Mexican States. It is divided into municipalities of Oaxaca, 570 munici ...
in 1919. Reko subsequently sent samples of teonanacatl (''Psilocybe mexicana'') as well as '' Ipomoea violacea'' (morning glory) seeds to Swedish anthropologist Henry Wassén in 1937. Reko had obtained the mushroom sample from Austrian
engineer Engineers, as practitioners of engineering, are professionals who Invention, invent, design, build, maintain and test machines, complex systems, structures, gadgets and materials. They aim to fulfill functional objectives and requirements while ...
Robert Weitlaner who was working in
Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
. Eventually, Wassén forwarded Reko and Weitlaner's mushroom sample to
Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...
, where the mushrooms came to the attention of American ethnobotanist Richard Evans Schultes. However, they had decomposed so badly that they could not be identified. Prior to Wassén obtaining specimens around 1936, the existence of teonanacatl was very controversial and was debated and even denied by some. In 1938, a small group of Westerners, which included Weitlaner's daughter and American anthropologist Jean Basset Johnson, attended a mushroom ceremony. They were the first Westerners known to do so and described the event. Schultes published reviews of teonanacatl being a hallucinogenic mushroom in the late 1930s.Schultes, R. E. (1939). The identifications of teonanácatl, a narcotic basidiomycete of the Aztecs. ''Botanical Museum Leaflets'', Harvard University, 7, 37–55. Schultes obtained specimens of three of the hallucinogenic mushrooms used in ceremonies, including '' Psilocybe caerulescens'', '' Panaeolus campanulatus'', and '' Stropharia cubensis'', but further investigations of the mushrooms were interrupted by
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
. Ergine (lysergic acid amide; LSA) and isoergine (isolysergic acid amide; iso-LSA) were first identified from
hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...
of ergot alkaloids in 1932 and 1936, respectively. In 1938,
Swiss Swiss most commonly refers to: * the adjectival form of Switzerland * Swiss people Swiss may also refer to: Places * Swiss, Missouri * Swiss, North Carolina * Swiss, West Virginia * Swiss, Wisconsin Other uses * Swiss Café, an old café located ...
chemist Albert Hofmann, working at Sandoz Laboratories, synthesized
lysergic acid diethylamide Lysergic acid diethylamide, commonly known as LSD (from German ; often referred to as acid or lucy), is a Semisynthesis, semisynthetic, Hallucinogen, hallucinogenic compound derived from ergot, known for its powerful psychological effects and ...
(LSD), a synthetic
derivative In mathematics, the derivative is a fundamental tool that quantifies the sensitivity to change of a function's output with respect to its input. The derivative of a function of a single variable at a chosen input value, when it exists, is t ...
of ergine, while developing new oxytocic
drug A drug is any chemical substance other than a nutrient or an essential dietary ingredient, which, when administered to a living organism, produces a biological effect. Consumption of drugs can be via insufflation (medicine), inhalation, drug i ...
s derived from ergot. LSD was not further investigated and was placed in storage for 5years. In 1943 however, Hofmann worked with LSD again and accidentally discovered its hallucinogenic effects when minute amounts of the potent psychedelic absorbed through his skin. His subsequent self-experiment with LSD three days later on April 19 is the psychedelic holiday Bicycle Day. Hofmann and his colleague,
psychiatrist A psychiatrist is a physician who specializes in psychiatry. Psychiatrists are physicians who evaluate patients to determine whether their symptoms are the result of a physical illness, a combination of physical and mental ailments or strictly ...
Werner Stoll, first described LSD in 1943 and first described its psychedelic effects in 1947. LSD began being distributed by Sandoz Laboratories for research purposes under the brand name Delysid in 1949. Schultes described the indigenous and shamanic use of
dimethyltryptamine Dimethyltryptamine (DMT), also known as ''N'',''N''-dimethyltryptamine (''N'',''N''-DMT), is a Psychedelic drug, serotonergic hallucinogen and Investigational New Drug, investigational drug of the substituted tryptamine, tryptamine family tha ...
(DMT)-containing psychedelic plants in 1954 and also described the use of hallucinogenic morning glories in the 1950s. The psychedelic effects of synthesized DMT were described by Hungarian chemist and psychiatrist Stephen Szára in 1956. Osmond described the hallucinogenic and other effects of morning glory seeds in clinical studies in 1955. Hofmann identified and described ergine and isoergine as the active constituents of morning glory seeds in 1960. Their hallucinogenic effects were first described by Hofmann in 1963. In 1952, couple and amateur ethnomycologists R. Gordon Wasson and Valentina Wasson learned of the ritual use of hallucinogenic mushrooms in the 16th century in Mexico from the published work of Schultes. They made several trips to Mexico in search of the mushrooms. In mid-1955, the Wassons participated in a mushroom ceremony with Mazatec curandera Maria Sabina in Huautla de Jiménez, Oaxaca, Mexico. Gordon Wasson published his experience in an article for ''
Life Life, also known as biota, refers to matter that has biological processes, such as Cell signaling, signaling and self-sustaining processes. It is defined descriptively by the capacity for homeostasis, Structure#Biological, organisation, met ...
'' magazine titled " Seeking the Magic Mushroom" in 1957, while Valentina Wasson published her experience as "I Ate the Sacred Mushroom" in '' This Week'' magazine the same year. Later in 1957, a second expedition was made by the Wassons to Mexico with French mycologist Roger Heim. Heim identified several of the mushrooms as belonging to the
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
''
Psilocybe ''Psilocybe'' ( ) is a genus of gilled mushrooms, growing worldwide, in the family Hymenogastraceae. Many species contain the Psychedelic drug, psychedelic compounds psilocybin and psilocin. Taxonomy Taxonomic history A 2002 study of the ...
''. They collected samples of the mushrooms and Heim sent a sample to Hofmann. Hofmann identified psilocybin as the active constituent in 1958 and developed a
chemical synthesis Chemical synthesis (chemical combination) is the artificial execution of chemical reactions to obtain one or several products. This occurs by physical and chemical manipulations usually involving one or more reactions. In modern laboratory uses ...
for it. Sandoz Pharmaceuticals began distributing tablets of psilocybin under the brand name Indocybin in 1960. French scientists Césaire Phisalix and Gabriel Bertrand isolated bufotenin from '' Bufo'' toads in 1893 and named it.Bochner, R., & Goyffon, M. (2007). L’œuvre scientifique de Césaire Phisalix (1852-1906), découvreur du sérum antivenimeux. Bull Soc Herp Fr, 123, 15-46. https://www.icict.fiocruz.br/sites/www.icict.fiocruz.br/files/L%20oeuvre%20scientifique%20de%20Cesaire%20Phisalix%20(1852--1906)%20decouvreur%20du%20serum%20antivenimeux.pdfPhisalix C, Bertrand G (1893) Toxicité comparée du sang et du venin de crapaud commun, considérée au point de vue de la sécrétion interne des glandes cutanées de cet animal. C R Soc Biol 45:477–479. https://scholar.google.com/scholar?cluster=14905926340091797397 The compound was first isolated to purity by Austrian chemist Hans Handovsky in 1920. Clinical studies assessed the effects of bufotenin and were published starting in 1956. However, the findings of these studies were conflicting, and bufotenin developed a long-standing reputation of being inactive and toxic. American ethnobotanist Jonathan Ott and colleagues subsequently showed in 2001 that bufotenin is in fact a psychedelic and does not necessarily produce major adverse effects, although marked
nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. It can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the throat. Over 30 d ...
and
vomiting Vomiting (also known as emesis, puking and throwing up) is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenteritis, pre ...
are prominent. The related psychedelic 5-MeO-DMT was first synthesized by Japanese chemists Toshio Hoshino and Kenya Shimodaira in 1935. It was later isolated from '' Dictyoloma incanescens'' in 1959. Subsequently, 5-MeO-DMT was isolated from numerous other plants and fungi. The compound was isolated from the skin of toads, specifically the Colorado River toad (''Incilius alvarius'', formerly ''Bufo alvarius''), by Italian chemist and pharmacologist Vittorio Erspamer in 1967. A 1984 pamphlet by Albert Most (real name Ken Nelson), titled '' Bufo Alvarius: the Psychedelic Toad of the Sonoran Desert'', described how to obtain and use Colorado River toad secretions as a psychedelic drug, and this started its recreational use.


Mid-20th-century research, popularization, and prohibition

Extensive clinical research on almost exclusively LSD, mescaline, and psilocybin was conducted in the 1950s and 1960s. However, the amount of research done on psilocybin was nowhere near that of LSD. Psychedelics like LSD started to become more visible in the mainstream sphere in the 1950s. English writer
Aldous Huxley Aldous Leonard Huxley ( ; 26 July 1894 – 22 November 1963) was an English writer and philosopher. His bibliography spans nearly 50 books, including non-fiction novel, non-fiction works, as well as essays, narratives, and poems. Born into the ...
tried mescaline, which he had obtained from English psychiatrist Humphry Osmond, in 1953, and described its effects in his 1954 book '' The Doors of Perception''.
British British may refer to: Peoples, culture, and language * British people, nationals or natives of the United Kingdom, British Overseas Territories and Crown Dependencies. * British national identity, the characteristics of British people and culture ...
politician A politician is a person who participates in Public policy, policy-making processes, usually holding an elective position in government. Politicians represent the people, make decisions, and influence the formulation of public policy. The roles ...
Christopher Mayhew tried mescaline in 1955 and this was reported on in the media. Osmond, in correspondence with Huxley, coined the term "psychedelic", meaning "mind-manifesting", in 1956. Psychedelics became widely recreationally used by the public, for instance by the hippies, during the
counterculture of the 1960s The counterculture of the 1960s was an anti-establishment cultural phenomenon and political movement that developed in the Western world during the mid-20th century. It began in the early 1960s, and continued through the early 1970s. It is ofte ...
. Harvard psychologists Timothy Leary and Richard Alpert began studying LSD and psilocybin in the early 1960s and ended up being fired from the university in 1963. Sandoz Laboratories ceased distribution of Delysid in 1965. Psychedelics became controlled substances in the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
and internationally in the 1960s and 1970s. By the end of the 1960s, psychedelic clinical research throughout the world had largely ceased. Besides public research, it was eventually learned that the United States government had also conducted research into psychedelics, as possible mind-control and truth-serum drugs, in the 1940s through the 1970s, for instance Project MKUltra by the
Central Intelligence Agency The Central Intelligence Agency (CIA; ) is a civilian foreign intelligence service of the federal government of the United States tasked with advancing national security through collecting and analyzing intelligence from around the world and ...
(CIA) and the Edgewood Arsenal research by the U.S. Army.


Creation of other synthetic psychedelics

The psychedelic effects of 3,4-methylenedioxyamphetamine (MDA), a synthetic analogue of mescaline that had been derived from
amphetamine Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...
in 1910, were discovered by American chemist and pharmacologist Gordon Alles in 1930, but weren't subsequently described by him until 1959. 3,4,5-Trimethoxyamphetamine (TMA), another synthetic mescaline analogue, was first described in 1947 and its psychedelic effects were described in 1955. 2,4,5-Trimethoxyphenethylamine (2C-O), a synthetic positional isomer of mescaline, was synthesized and claimed to be psychedelic similarly to mescaline in 1931, but later trials found it to be inactive. Various synthetic tryptamine psychedelics, such as diethyltryptamine (DET), 4-PO-DET (CEY-19), and 4-HO-DET (CZ-74), were developed in the late 1950s. In addition, the synthetic α-alkyltryptamine analogues α-methyltryptamine (AMT; Indopan) and α-ethyltryptamine (AET; Monase), which are psychedelics and/or
entactogen Entactogens, also known as empathogens or connectogens, are a class of psychoactive drugs that induce the production of experiences of emotional communion, oneness, connectedness, emotional openness—that is, empathy—as particularly observe ...
s, were marketed and clinically used at non-hallucinogenic doses as
antidepressant Antidepressants are a class of medications used to treat major depressive disorder, anxiety disorders, chronic pain, and addiction. Common side effects of antidepressants include Xerostomia, dry mouth, weight gain, dizziness, headaches, akathi ...
s in the early 1960s, but were quickly withdrawn due to physical toxicity. Numerous synthetic psychedelic tryptamines were known by the mid-1970s. Alexander Shulgin, an American chemist working at Dow Chemical Company, tried mescaline by 1960. This experience has been described as "the most consequential mescaline trip of the sixties", as it caused Shulgin to redirect his focus and life's work to psychedelic chemistry. Starting in the 1960s, Shulgin synthesized and gradually described hundreds of novel synthetic psychedelics as well as entactogens in scientific publications and published books such as ''
PiHKAL ''PiHKAL: A Chemical Love Story'' is a book by Alexander Shulgin and Ann Shulgin published in 1991. The subject of the work is Psychoactive drug, psychoactive phenethylamine Derivative (chemistry), chemical derivatives, notably those that act ...
'' (1991) and '' TiHKAL'' (1997). Notable major examples of these drugs have included the DOx psychedelic DOM, the 2C psychedelic 2C-B, and the MDxx entactogen
MDMA 3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor Psychedelic drug, psychedelic properties. In studies, it has been used ...
, among others. However, MDMA was not an original creation of Shulgin's but had previously been first synthesized in 1912 and had surfaced as a recreational drug related to MDA by the mid- to late-1960s. Instead, Shulgin had merely served to help popularize and spread awareness about MDMA and its unique effects. MDMA became outlawed in the mid-1980s. In response to this, the Multidisciplinary Association for Psychedelic Studies (MAPS) was founded by Rick Doblin in 1986 and began efforts to develop MDMA and other psychedelics as medicines. American chemist David E. Nichols has developed numerous novel psychedelics and entactogens from the 1970s to present.
Swiss Swiss most commonly refers to: * the adjectival form of Switzerland * Swiss people Swiss may also refer to: Places * Swiss, Missouri * Swiss, North Carolina * Swiss, West Virginia * Swiss, Wisconsin Other uses * Swiss Café, an old café located ...
chemist Daniel Trachsel, sometimes referred to as the "German Shulgin", has also developed and published numerous novel psychedelics as well as entactogens since the 1990s.
NBOMe The 25-NB (25''x''-NB''x'') series, or NBOMe series, also known as the ''N''-benzylphenethylamines, is a family of serotonergic psychedelics. They are substituted phenethylamines and were derived from the 2C (psychedelics), 2C family. The most c ...
psychedelics such as 25I-NBOMe, derived from structural modification of 2C psychedelics, were first described by Ralf Heim and colleagues by 2000. The NBOMe drugs were subsequently encountered as novel recreational drugs by 2010, and by 2012 had eclipsed other psychedelics like LSD and psilocybin-containing mushrooms in popularity, at least for a time.


Psychedelics, serotonin, and their actions

Serotonin Serotonin (), also known as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter with a wide range of functions in both the central nervous system (CNS) and also peripheral tissues. It is involved in mood, cognition, reward, learning, ...
, also known as 5-hydroxytryptamine (5-HT) and originally called enteramine, was discovered by Vittorio Erspamer in the 1930s and its structural identity was fully characterized in the late 1940s and early 1950s. Serotonin was discovered in the
brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...
by Betty Twarog and Irvine Page in 1953. It was quickly noticed that LSD contains the serotonin-like tryptamine scaffold within its
chemical structure A chemical structure of a molecule is a spatial arrangement of its atoms and their chemical bonds. Its determination includes a chemist's specifying the molecular geometry and, when feasible and necessary, the electronic structure of the target m ...
. Shortly thereafter, it was found that LSD showed serotonin-like effects and could antagonize serotonin in certain
assay An assay is an investigative (analytic) procedure in laboratory medicine, mining, pharmacology, environmental biology and molecular biology for qualitatively assessing or quantitatively measuring the presence, amount, or functional activity ...
s. Studies in the 1960s and 1970s showed that various serotonin antagonists could block the behavioral effects of psychedelics in animals. The serotonin receptors, including the serotonin 5-HT2 receptors, were elucidated by the late 1970s. Mediation of the hallucinogenic effects of psychedelics by serotonin 5-HT2 receptor
agonism Agonism (from Greek 'struggle') is a political and social theory that emphasizes the potentially positive aspects of certain forms of conflict. It accepts a permanent place for such conflict in the political sphere, but seeks to show how indivi ...
was proposed by Richard Glennon and other researchers by the early 1980s. The human serotonin 5-HT2A receptor was first cloned in 1990. The hallucinogenic effects of psilocybin in humans were shown to be blocked by the selective serotonin 5-HT2A receptor antagonist ketanserin by Franz Vollenweider and colleagues in 1998, solidifying theoretical notions that agonism of the serotonin 5-HT2A receptor mediates the hallucinogenic effects of serotonergic psychedelics.


Psychedelic renaissance

Since the prohibition of the 1960s and 1970s, clinical research into psychedelics started to resume by the 1990s, for instance the studies of DMT by Rick Strassman, and they have once again started to be developed as
pharmaceutical drug Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy ( pharmacotherapy) is an important part of the ...
s for potential medical use. A so-called "psychedelic renaissance", in which interest in psychedelics has resurged, began in the late 2010s and early 2020s. Michael Pollan's 2018 book '' How to Change Your Mind'', which was also adapted into a Netflix series in 2022, was especially impactful in terms of increasing mainstream awareness and interest in psychedelics. More than 100clinical trials of four major psychedelics, including psilocybin, LSD, ayahuasca, and
MDMA 3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor Psychedelic drug, psychedelic properties. In studies, it has been used ...
, were identified as being underway in 2024.


Society and culture


Etymology and nomenclature

The term '' psychedelic'' was coined by the psychiatrist Humphrey Osmond during written correspondence with author
Aldous Huxley Aldous Leonard Huxley ( ; 26 July 1894 – 22 November 1963) was an English writer and philosopher. His bibliography spans nearly 50 books, including non-fiction novel, non-fiction works, as well as essays, narratives, and poems. Born into the ...
(written in a rhyme: “To fathom Hell or soar angelic/Just take a pinch of psychedelic.”) and presented to the New York Academy of Sciences by Osmond in 1957. It is irregularly derived from the Greek words ψυχή (''psychḗ'', meaning 'mind, soul') and δηλείν (''dēleín'', meaning 'to manifest'), with the intended meaning "mind manifesting" or alternatively "soul manifesting", and the implication that psychedelics can reveal unused potentials of the human mind. The term was loathed by American ethnobotanist Richard Schultes but championed by American psychologist Timothy Leary. Aldous Huxley had suggested his own coinage ''phanerothyme'' (Greek ''phaneroein''- "to make manifest or visible" and Greek ''thymos'' "soul", thus "to reveal the soul") to Osmond in 1956. Recently, the term entheogen (meaning "that which produces the divine within") has come into use to denote the use of psychedelic drugs, as well as various other types of psychoactive substances, in a religious, spiritual, and mystical context. In 2004, David E. Nichols wrote the following about the nomenclature used for psychedelic drugs: Robin Carhart-Harris and Guy Goodwin write that the term ''psychedelic'' is preferable to ''hallucinogen'' for describing classical psychedelics because of the term ''hallucinogen''s "arguably misleading emphasis on these compounds' hallucinogenic properties." While the term ''psychedelic'' is most commonly used to refer only to serotonergic hallucinogens, it is sometimes used for a much broader range of drugs, including empathogen–entactogens, dissociatives, and atypical hallucinogens/psychoactives such as ''
Amanita muscaria ''Amanita muscaria'', commonly known as the fly agaric or fly amanita, is a basidiomycete fungus of the genus ''Amanita''. It is a large white-lamella (mycology), gilled, white-spotted mushroom typically featuring a bright red cap covered with ...
'', ''
Cannabis sativa ''Cannabis sativa'' is an annual Herbaceous plant, herbaceous flowering plant. The species was first classified by Carl Linnaeus in 1753. The specific epithet ''Sativum, sativa'' means 'cultivated'. Indigenous to East Asia, Eastern Asia, the pla ...
'', '' Nymphaea nouchali'' and '' Salvia divinorum''. Thus, the term ''serotonergic psychedelic'' is sometimes used for the narrower class. It is important to check the definition of a given source. This article uses the more common, narrower definition of ''psychedelic''.


Surrounding culture

Psychedelic culture includes manifestations such as
psychedelic music Psychedelic music (sometimes called psychedelia) is a wide range of popular music styles and genres influenced by 1960s psychedelia, a subculture of people who used psychedelic drugs such as Dmt, DMT, Lysergic acid diethylamide, LSD, mescaline, ...
, psychedelic art, psychedelic literature, psychedelic film, and psychedelic festivals.St John, Graham
"Neotrance and the Psychedelic Festival."
''Dancecult: Journal of Electronic Dance Music Culture,'' 1(1) (2009).
Examples of psychedelic music are found in the work of 1960s rock bands like the
Grateful Dead The Grateful Dead was an American rock music, rock band formed in Palo Alto, California, in 1965. Known for their eclectic style that fused elements of rock, blues, jazz, Folk music, folk, country music, country, bluegrass music, bluegrass, roc ...
,
Jefferson Airplane Jefferson Airplane was an American Rock music, rock band formed in San Francisco, California, in 1965. One of the pioneering bands of psychedelic rock, the group defined the San Francisco Sound and was the first from the San Francisco Bay Area, ...
, The 13th Floor Elevators, and Syd Barrett-era
Pink Floyd Pink Floyd are an English Rock music, rock band formed in London in 1965. Gaining an early following as one of the first British psychedelic music, psychedelic groups, they were distinguished by their extended compositions, sonic experiments ...
. Many psychedelic bands and elements of the psychedelic subculture originated in
San Francisco San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...
during the mid to late 1960s.


Legal status

Many psychedelics are classified under Schedule I of the United Nations Convention on Psychotropic Substances of 1971 as drugs with the greatest potential to cause harm and no acceptable medical uses. In addition, many countries have analogue laws; for example, in the United States, the Federal Analogue Act of 1986 automatically forbids any drugs sharing similar chemical structures or chemical formulas to prohibited substances if sold for human consumption. In July 2022, though, under the United States Food and Drug Administration, the drug psilocybin was on track to be approved of as a treatment for depression, and MDMA as a treatment for post-traumatic stress disorder. U.S. states such as Oregon and Colorado have also instituted decriminalization and legalization measures for accessing psychedelics and states like New Hampshire are attempting to do the same. J.D. Tuccille argues that increasing rates of use of psychedelics in defiance of the law are likely to result in more widespread legalization and decriminalization of access to the substances in the United States (as has happened with
alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...
and
cannabis ''Cannabis'' () is a genus of flowering plants in the family Cannabaceae that is widely accepted as being indigenous to and originating from the continent of Asia. However, the number of species is disputed, with as many as three species be ...
).


Research


Therapeutic effects

Psychedelic substances which may have therapeutic uses include psilocybin, LSD, and mescaline. During the 1950s and 1960s, lack of
informed consent Informed consent is an applied ethics principle that a person must have sufficient information and understanding before making decisions about accepting risk. Pertinent information may include risks and benefits of treatments, alternative treatme ...
in some scientific trials on psychedelics led to significant, long-lasting harm to some participants. Since then, research regarding the effectiveness of psychedelic therapy has been conducted under strict ethical guidelines, with fully informed consent and a pre-screening to avoid people with psychosis taking part. Although the history behind these substances has hindered research into their potential medicinal value, scientists are now able to conduct studies and renew research that was halted in the 1970s. Some research has shown that these substances have helped people with such mental disorders as obsessive-compulsive disorder (OCD),
post-traumatic stress disorder Post-traumatic stress disorder (PTSD) is a mental disorder that develops from experiencing a Psychological trauma, traumatic event, such as sexual assault, domestic violence, child abuse, warfare and its associated traumas, natural disaster ...
(PTSD), alcoholism, depression, and cluster headaches. It has long been known that psychedelics promote neurite growth and
neuroplasticity Neuroplasticity, also known as neural plasticity or just plasticity, is the ability of neural networks in the brain to change through neurogenesis, growth and reorganization. Neuroplasticity refers to the brain's ability to reorganize and rewir ...
and are potent
psychoplastogen Psychoplastogens, also known as neuroplastogens, are a group of Small molecule#Drugs, small molecule drugs that produce rapid and sustained effects on neuronal structure and function, intended to manifest therapeutic benefit after a single admin ...
s. There is evidence that psychedelics induce molecular and cellular adaptations related to neuroplasticity and that these could potentially underlie therapeutic benefits. Psychedelics have also been shown to have potent
anti-inflammatory Anti-inflammatory is the property of a substance or treatment that reduces inflammation, fever or swelling. Anti-inflammatory drugs, also called anti-inflammatories, make up about half of analgesics. These drugs reduce pain by inhibiting mechan ...
activity and therapeutic effects in animal models of inflammatory diseases including
asthma Asthma is a common long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wh ...
,
cardiovascular disease Cardiovascular disease (CVD) is any disease involving the heart or blood vessels. CVDs constitute a class of diseases that includes: coronary artery diseases (e.g. angina, heart attack), heart failure, hypertensive heart disease, rheumati ...
, and
diabetes Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or the cells of th ...
. They might also be useful for the treatment of neuroinflammation as well as post-COVID-19 syndrome (long COVID).


See also

* Bwiti * Cognitive liberty * Concord Prison Experiment * Designer drug * Dissociative drug * Deliriant * Drug harmfulness * Hallucinogenic fish * Hallucinogenic plants in Chinese herbals * ''Hamilton's Pharmacopeia'' * Ibogaine * Marsh Chapel Experiment * Mystical psychosis * Psychedelia (film), ''Psychedelia'' * Serotonergic cell groups * '' Tabernanthe iboga'' * Trip report


References


Further reading

* * * * * * * Winstock, Ar; Timmerman, C; Davies, E; Maier, Lj; Zhuparris, A; Ferris, Ja; Barratt, Mj; Kuypers, Kpc (2021).
Global Drug Survey (GDS) 2020 Psychedelics Key Findings Report
'.


External links


Psychedelic Timeline - Tom Frame - Psychedelic Times

Psychedelic drugs - Massviews Analysis - Wikipedia
{{Chemical classes of psychoactive drugs 5-HT2A agonists Drug classes defined by psychological effects Hallucinations Psychedelic drugs,