Autism spectrum

Autism, also known as autism spectrum disorder (ASD), is a neurodevelopmental disorder characterized by differences or difficulties in social communication and interaction, a preference for predictability and routine, sensory processing differences, focused interests, and repetitive behaviors, which may include stimming. Formal diagnosis requires significant challenges in multiple domains of life, with characteristics that are atypical or more pronounced than expected for one's age and sociocultural context.(World Health Organization: International Classification of Diseases version 11 (ICD-11)): https://icd.who.int/browse/2024-01/mms/en#437815624 Motor coordination difficulties are common but not required for diagnosis. Autism is a spectrum disorder, resulting in wide variations in presentation and support needs, such as that between speaking and non-speaking populations.

Increased estimates of autism prevalence since the 1990s are primarily attributed to broader criteria and increased awareness, although a true rise in prevalence is possible. The World Health Organization estimates about 1 in 100 children were diagnosed between 2012 and 2021, noting an increasing trend. This rise has fueled anti-vaccine activists' disproven claim that vaccines cause autism. While precise causes are mostly unknown, research shows that autism is highly heritable and polygenic. Environmental factors play a relatively small role, mainly prenatally. Boys are diagnosed significantly more often than girls. Autism frequently co-occurs with attention deficit hyperactivity disorder (ADHD), epilepsy, and intellectual disability.

There is no known cure for autism, and there are advocates who oppose pursuing one. Interventions such as applied behavior analysis, speech therapy, and occupational therapy can help increase self-care, social, and language skills. Reducing environmental and social barriers enables autistic people to participate more fully in education, employment, and other aspects of life. Medications can alleviate some co-occurring problems.

The view of autism as a disorder has been challenged by the neurodiversity paradigm, which frames autistic traits as a healthy variation of the human condition. This view is supported by the autism rights movement, whose paradigm researchers have recently increasingly adopted. The neurodiversity framework has sparked significant debate and controversy among autistic people, advocacy groups, healthcare providers, and charities.

Classification

The diagnostic manuals DSM-5 and ICD-11 define autism as a highly variable neurodevelopmental disorder that is generally thought to cover a broad and deep spectrum, manifesting very differently from one person to another. Some have high support needs, may be non-speaking, and experience developmental delays; this is more likely with other co-existing diagnoses. Others may have more typical speech-language and intellectual skills but atypical social/conversation skills, focused interests, and wordy, pedantic communication. They may still require significant support in some areas of their lives. The spectrum model should not be understood as a continuum running from mild to severe, but instead means that autism can present very differently in each person, with support needs depending on context and changing over time.

Before the DSM-5 (2013) and ICD-11/ICD-11 CDDR (2019/2024) diagnostic manuals were adopted, autism was found under the diagnostic category pervasive developmental disorder. The previous system relied on a set of closely related and overlapping diagnoses such as Asperger syndrome and the diagnosis formerly known as classic autism, Kanner syndrome, or childhood autism. This created unclear boundaries between the terms, so for the DSM-5 and ICD-11, a spectrum approach was taken. The new system is also more restrictive, meaning fewer people qualify for diagnosis.

While the DSM and ICD greatly influence each other, there are differences. The ICD and the DSM change over time, and there has been collaborative work toward a convergence of the two since 1980 (when DSM-III was published and ICD-9 was current), including efforts to better integrate findings from biological research and a move toward simpler classification systems, while diagnosis continues to rely primarily on behavioral criteria. The DSM-5 and ICD-11 use different categorization tools to define the autism spectrum. DSM-5 uses a "level" system, which specifies the level of support the person needs. In this system, level 1 is the mildest form and level 3 the most severe. In contrast, the ICD-11 system uses two separate factors, intellectual impairment and language impairment, as these are seen as the most crucial.

As of 2023, empirical and theoretical research highlights how established autism criteria may be ineffective descriptors of autism as a whole, encouraging alternative research approaches, such as returning to autism prototypes, exploring new causal models of autism, or developing transdiagnostic endophenotypes. Some proposed alternatives to the disorder-focused spectrum model deconstruct autism into separate phenomena: (1) a non-pathological spectrum of behavioral traits in the population, (2) the effect of rare genetic mutations and environmental factors potentially leading to neurodevelopmental and psychological conditions. The National Guideline for autism from the Australian CRC recommends switching to a neurodiversity-affirming framework that does not view autism as a disorder while still recognizing the disability that many autistic people experience. Language guidelines from the US' National Institutes of Health and the UK's National Health Service also recommend talking about autism in less pathologizing terms, e.g. "characteristics" instead of "symptoms", "likelihood" instead of "risk", and avoiding terms like "treatment", "cure", or "prevention".

ICD

The World Health Organization's International Classification of Diseases (11th revision), ICD-11, was released in June 2018 and came into full effect as of January 2022. It describes autism spectrum disorder (ASD) as follows:

DSM

The American Psychiatric Association's ''Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision'' (DSM-5-TR), released in 2022, is the current version of the DSM. Its fifth edition, DSM-5, released in May 2013, was the first to define ASD as a single diagnosis, which is still the case in the DSM-5-TR. ASD encompasses previous diagnoses, including the four traditional diagnoses of autism— classic autism, Asperger syndrome, childhood disintegrative disorder, and pervasive developmental disorder not otherwise specified (PDD-NOS)—and the range of diagnoses that included the word "autism". Rather than distinguishing among these diagnoses, the DSM-5 and DSM-5-TR adopt a dimensional approach, with one diagnostic category for disorders that fall under the autism spectrum umbrella. Within that category, the DSM-5 has a framework that differentiates each person by dimensions of symptom severity and by associated features (i.e., the presence of other conditions or factors that likely contribute to the symptoms, other neurodevelopmental or mental conditions, intellectual disability, or language impairment). The symptom domains are (a) social communication and (b) restricted, repetitive behaviors, and there is the option of specifying a separate severity—the negative effect of the symptoms on the person—for each domain, rather than just overall severity. Before the DSM-5, the DSM separated social deficits and communication deficits into two domains. Further, the DSM-5 changed to an onset age in the early developmental period, with a note that symptoms may manifest later when social demands exceed capabilities, rather than the previous, more restricted three years of age. These changes remain in the DSM-5-TR.

Signs and characteristics

Pre-diagnosis

Autism is primarily characterized by differences and difficulties in social interaction and communication, alongside restricted or repetitive patterns of interests, activities, and behaviors ( stimming), and in many cases distinctive reactions to sensory input. The specific presentation varies widely. For many autistic people, characteristics first appear during infancy or childhood and continue lifelong. Autistic people may be significantly disabled in some respects but average, or even superior, in others.

Clinicians often consider assessment for autism when these types of characteristics are present, especially if they are associated with difficulties in obtaining or sustaining employment or education, difficulties in initiating or sustaining social relationships, involvement with mental health or learning disability services, or a history of neurodevelopmental conditions (including learning disabilities and ADHD) or mental health conditions.

In the social domain

Common signs of autism in the social domain include little or no babbling as an infant as well as limited eye contact; language skills developed later (e.g., having a smaller vocabulary than peers or difficulty expressing oneself in words); and less interest in other children or caretakers, possibly with more interest in objects. Difficulty may also be apparent in reciprocal social interactions, as in games like peek-a-boo or pat-a-cake, as well as in shared attention to objects of interest.

Restricted, repetitive behaviors

Repetition of words or phrases, including echolalia, as well as repetitive movements are commonly found in autistic people. Rigid routines and aversion to change are also common signs, and autistic people often have a very specific area of interest. Other signs include playing with toys in ways considered limited or unusual (e.g., lining up toys) and distinctive reactions to smells, textures, sounds, tastes, or appearances.

Social and communication skills

Autistic people experience impairments in social communication and interaction. The current social criteria for autism diagnosis require people to have difficulties across three social domains: social-emotional reciprocity, nonverbal communication, and developing and sustaining relationships.

Social-emotional reciprocity

Historically, autistic children were said to be delayed in developing a theory of mind, and the empathizing–systemizing theory has argued that while autistic people have compassion ( affective empathy) for others with similar autistic features, they have limited, though not necessarily absent, cognitive empathy. This may present as social naïvety, lower than average intuitive perception of the utility or meaning of body language, social reciprocity, or social expectations, including the habitus, social cues, and some aspects of sarcasm, which to some degree may also be due to co-occurring alexithymia. Recent research has increasingly questioned these findings, as the double empathy problem theory (2012) argues that there is a lack of mutual understanding and empathy between both non-autistic and autistic individuals.

Thus there has been a recent shift to acknowledge that autistic people may simply respond and behave differently than non-autistic people. So far, research has identified two unconventional features by which autistic people create shared understanding ( intersubjectivity): "a generous assumption of common ground that, when understood, led to rapid rapport, and, when not understood, resulted in potentially disruptive utterances; and a low demand for coordination that ameliorated many challenges associated with disruptive turns". Autistic interests, and thus conversational topics, seem to be largely driven by an intense interest in specific topics ( monotropism). Two studies found that autistic–autistic interactions are as effective in information transfer as interactions between non-autistics are.

Nonverbal communication

Autistic people display atypical nonverbal behaviors or show differences in nonverbal communication. They may make infrequent eye contact, even when called by name, or avoid it altogether. This is because they find it uncomfortable, distracting, or disturbing, and may also be due to the high amount of sensory input received when making eye contact. Autistic people often recognize fewer emotions and their meaning from others' facial expressions, and may not respond with facial expressions expected by their non-autistic peers. Temple Grandin, an autistic woman involved in autism activism, described her inability to understand neurotypicals' social communication as leaving her feeling "like an anthropologist on Mars". Autistic people struggle to understand the social context and subtext of neurotypical conversational or printed situations, and form different conclusions about the content. Autistic people may not control the volume of their voice in different social settings. At least half of autistic children have atypical prosody.

Developing and sustaining relationships

What may look like self-involvement or indifference to non-autistic people stems from autistic differences in recognizing other people's personalities, perspectives, and interests. Most published research focuses on the interpersonal relationship difficulties between autistic people and their non-autistic counterparts and how to solve them through teaching neurotypical social skills, but newer research has also evaluated what autistic people want from friendships, such as a sense of belonging and benefits to mental health. Children on the autism spectrum are more frequently involved in bullying situations than their non-autistic peers, and mostly experience bullying as victims rather than perpetrators or victim-perpetrators. For autistic people who have a desire for friendships, lower friendship quantity and quality often leads to increased loneliness. As they progress through life, autistic people observe and form models of social patterns, and develop coping mechanisms, some of which are referred to as " masking". Masking is associated with worse mental health outcomes as well as later diagnosis, which prevents the autistic person from accessing needed supports.

Restricted and repetitive behaviors

The second core feature of autism is a pattern of restricted and repetitive behaviors, activities, and interests. To be diagnosed with autism under the DSM-5-TR, a person must have at least two of the following behaviors:

* Repetitive behaviors: repetitive behaviors such as rocking, hand flapping, finger flicking, head banging, or repeating phrases or sounds. These behaviors may occur constantly or only when the person is stressed, anxious, or upset. They are also known as stimming.
* Resistance to change: strict adherence to routines such as eating certain foods in a specific order or taking the same path to school every day. The person may become distressed if their routine changes or is disrupted.
* Restricted interests: intense interest in a particular activity, topic, or hobby, and devoting all one's attention to it. For example, young children might completely focus on things that spin and ignore everything else. Older children might try to learn everything about a single topic, such as the weather or sports, and perseverate or talk about it constantly.
* Sensory reactivity: an unusual reaction to certain sensory inputs, such as aversion to specific sounds or textures, fascination with lights or movements, or apparent indifference to pain or heat.

It is increasingly argued that these characteristics should be accepted, which is supported by their recognized functions, such as self-regulation. Focused interests can also offer significant personal fulfillment and foster the development of specialized knowledge. A distinction must be made between these features and those of obsessive–compulsive disorder, which can co-occur with autism and involves distressing compulsions or obsessions aimed at preventing feared negative events.

Speaking, minimally speaking, non-speaking

Differences in verbal communication become noticeable in childhood, as many autistic children develop language skills at an uneven pace. Verbal communication may develop later or never ( non-speaking autism), while reading ability may be present before school age ( hyperlexia). Less joint attention may distinguish autistic from non-autistic infants. Infants may show later onset of babbling, unusual gestures, lower responsiveness, and vocal patterns that are not synchronized with the caregiver. In their second and third years, autistic children may have less frequent and less diverse babbling, consonants, words, and word combinations, and their gestures may be less often integrated with words. Autistic children are less likely to make requests or share experiences and more likely to simply repeat others' words ( echolalia). The CDC estimated in 2015 that around 40% of autistic children do not speak at all. Autistic adults' verbal communication skills largely depend on when and how well speech is acquired during childhood.

Mental health, self-injury, and suicide

Self-injurious behavior (SIB) is approximately three times more common in autistic people than non-autistic people. These behaviors include head-banging, hand-biting, and skin-picking, and can lead to serious injury or, in rare cases, death. Multiple theories explore the development and persistence of SIB within developmental conditions, including autism. Explanations include communication difficulties, leading people to use self-injury as a way to express needs, distress, or other messages. Additionally, SIB may be linked to efforts to regulate sensory input or modulate pain perception, particularly for those experiencing chronic discomfort or medical conditions. Neurological factors are also under investigation, with anomalies in basal ganglia connectivity suggested as a potential biological predisposition in some autistic people.

Other risk factors for self-harm and suicidality include circumstances that could affect anyone, such as mental health problems (e.g., anxiety disorder) and social problems (e.g., unemployment and social isolation). In addition, there are autism-specific factors, such as exhausting attempts to behave like a neurotypical person to avoid stigma and negative reactions of neurotypical society towards autistic people ( masking). Autistic people are also at significantly increased risk of victimization, including bullying, sexual assault, and other forms of criminal abuse. Approximately 8 in 10 autistic people have a mental health problem in their lifetime, in comparison to 1 in 4 of the general population. A 2019 meta-analysis found autistic people to be four times more likely to have depression than non-autistic people, with approximately 40% of autistic adults having depression.

Rates of suicidality vary significantly depending upon what is being measured. This is partly because questionnaires developed for neurotypical subjects are not always valid for autistic people. As of 2023, the Suicidal Behaviours Questionnaire–Autism Spectrum Conditions (SBQ-ASC) is the only test validated for autistic people. According to some estimates, about a quarter of autistic youth and a third of all autistic people have experienced suicidal ideation at some point. Autistic people are about three times as likely as non-autistic people to make a suicide attempt. Almost 10% of autistic youth and 15% to 25% of autistic adults have attempted suicide. Rates of suicide attempts and suicidal ideation are the same for people formally diagnosed with autism and people who have typical intelligence and are believed to be autistic but have not been diagnosed. A study found the suicide rate for verbal autistics to be nine times that of the general population. The suicide risk is higher for autistic people who are not cisgender males and do not have intellectual disabilities.

Burnout, inertia, meltdown, shutdown

Autistic burnout is a prolonged state of exhaustion that results in reduced social and occupational skill capacity and quality of life. Autistic people have reported that this burnout can occur repeatedly, have cognitive and physical effects, be misunderstood by medical professionals, and adversely affect life goals in extended cases. Autistic people often cite burnout as a catalyst for autism diagnosis or improved self-care and well-being strategies. In particular, they have anecdotally identified factors that lead to burnout. Autistic people can also derive support from community members by sharing mitigating and coping strategies. This is a reason community psychology is used to study autistic communities.

Autistic inertia is described by autistic people as difficulty transitioning between activities or states. This can manifest both in starting (initiation difficulties) and finishing (persistence or difficulties in switching) tasks or actions. Those affected often report an inner sluggishness or inertia, even when they want to start or finish an action. Therefore, it is different from laziness or lack of motivation.

A meltdown may arise if an autistic person has to process too much information, resulting in anxiety and overwhelm. Triggers may be sensory or social, and include unpredictability, unmet basic needs, or emotional situations, and often accumulate. A meltdown can be expressed audibly (e.g., screaming or crying) or physically. These are not intentional actions and are thus not tantrums; the autistic person cannot express themself in any other way. The person often shows signs of distress beforehand, such as pacing, asking repetitive questions, trembling, or sweating. A shutdown is similar, but inward, and the autistic person is often unable to speak or withdraws completely. Meltdown or shutdown can be prevented by eliminating the distressing factors. They can be ameliorated by avoiding further questions or pressure, showing the person that one is there to help, and allowing the person to calm down by leaving the situation or breathing slowly.

Other features

Autistic people may exhibit traits or characteristics that are not part of the formal diagnostic criteria but can nonetheless affect their personal well-being or family dynamics. This paper represents a consensus of representatives from nine professional and four parent organizations in the US.
* Some autistic people show unusual or notable abilities, ranging from splinter skills (such as the memorization of trivia) to rare talents in mathematics, music, or artistic reproduction, which in exceptional cases are considered a part of the savant syndrome. One study describes how some autistic people show superior skills in perception and attention relative to the general population.
* More generally, autistic people tend to show a "spiky skills profile", with strong abilities in some areas contrasting with much weaker abilities in others.
* An estimated 60–80% of autistic people have motor signs that include poor muscle tone, poor motor planning, and toe walking; difficulties in motor coordination are pervasive across the autism spectrum.
* Pathological demand avoidance can occur. People with this set of autistic characteristics are more likely to refuse to do what is asked or expected of them, even to activities they enjoy.
* Unusual or atypical eating behavior occurs in about three-quarters of children on the autism spectrum, to the extent that it was formerly a diagnostic indicator. Selectivity is the most common characteristic, although eating rituals and food refusal also occur.

Digital media use

In his 2015 book '' NeuroTribes'', Steve Silberman highlights the emergence of online communities centered around autistic people, such as Autism Network International—founded by Jim Sinclair—and Wrong Planet. Silberman writes that these digital spaces offer a "natural home" for autistic people to communicate through written language. A 2022 systematic review of 21 studies found that most studies reported moderate correlations between autism, problematic internet use, and gaming disorder.

Caregivers

Families who care for an autistic child face greater stress. Parents may struggle to understand their child and to find appropriate care options. They can take a negative view of autism, and may struggle emotionally. Affiliate stigma also decreases quality of life, where negative attitudes toward the autistic child are extended to those close to the child. About 85% of autistic people need support with independent living in adulthood. Family members who are themselves autistic are often better able to understand the autistic child.

Co-occurring conditions

Autism is correlated or co-occurring with several conditions. Comorbidity may increase with age and may complicate the course of youth on the autism spectrum and make intervention and therapy more difficult. Distinguishing between autism and other diagnoses can be challenging because the traits of autism often overlap with symptoms of other conditions, and the characteristics of autism make traditional diagnostic procedures difficult., known as diagnostic overshadowing. Common co-occurring conditions are:
* ADHD is sometimes co-occurring with autism (25% to 32%). Characteristics similar to those of ADHD can be part of an autism diagnosis.
* Epilepsy occurs in about 10% of autistic people. The risk is higher for older autistic people and those with intellectual disability.
* Intellectual disabilities are some of the most common co-occurring conditions with autism (30% to 40%). As diagnosis is increasingly given to people with lower support needs, there is a tendency for the proportion with co-occurring intellectual disability to decrease over time.
* Various anxiety disorders tend to co-occur with autism, with overall co-occurring rates of 17% to 23%. Many anxiety disorders have characteristics that are better explained by autism itself or are hard to distinguish from autism's features.
* Rates of co-occurring depression in autistic people range from 9% to 13%.
* Obsessive–compulsive disorder (OCD) occurs in 7% to 10% of autistic people.
* Starting in adolescence, some autistic people fall under the criteria for the similar-looking schizoid personality disorder, which is characterized by a lack of interest in social relationships, a tendency toward a solitary or sheltered lifestyle, secretiveness, emotional coldness, detachment, and apathy.
* Genetic conditions: 10% to 15% of autism cases have an identifiable Mendelian (single-gene) condition, chromosome anomalies, or other genetic syndromes. An example is tuberous sclerosis, present in 1% to 4% of autistic people.
* Gastrointestinal problems are one of the most commonly co-occurring medical conditions in autistic people. These are linked to greater social difficulties, irritability, language difficulties, mood changes, distressed behavior, and sleep problems.
* Sleep problems affect about two-thirds of autistic people at some point in childhood. These most commonly include symptoms of insomnia, such as difficulty falling asleep, frequent nocturnal awakenings, and early-morning awakenings. Sleep problems are associated with difficult behaviors and family stress, and are often a focus of clinical attention over and above the autism diagnosis.
* Motor difficulties, including features of dyspraxia, are highly prevalent in autistic people, and there is a significant association between autism and joint hypermobility, which is also linked to Ehlers-Danlos Syndromes (EDS).
* A 2024 Danish cohort study found increased risks for a multitude of co-occurring physical diseases, especially in infancy.
* There is tentative evidence that gender dysphoria occurs more frequently in autistic people.

Management

Currently, there is no cure for autism. People in the autistic community have expressed support for the neurodiversity perspective's opposition to seeking a cure. From the perspective of neurodiversity, "curing" or otherwise treating autism may not be an appropriate goal.

Interventions targeting specific challenges or co-occurring conditions associated with autism are widely regarded as important. Perspectives on the goals of these interventions vary: the medical model of disability often focuses on addressing core characteristics such as social communication difficulties and restricted/repetitive behaviors. The neurodiversity movement supports interventions aimed at enhancing functional communication (spoken or non-spoken), managing related issues like anxiety or inertia, or addressing behaviors considered harmful, rather than seeking to alter core autistic features.

Some report that those with limited support needs are likely to have lessened autistic features over time, while others argue that this perception is likely due to masking, hiding autistic characteristics to avoid stigma. Factors such as developing spoken language before age six, having an IQ above 50, and possessing marketable skills are associated with a higher likelihood of independent living in adulthood. Studies of interventions have methodological problems that prevent definitive conclusions about efficacy, but the development of evidence-based interventions has advanced.

Several therapies can help autistic children, and they are typically tailored to the child's needs. The main goals of therapy are to lessen associated difficulties and family distress, and to increase quality of life and functional independence. In general, higher IQs correlate with higher responsiveness to interventions and larger intervention outcomes. Behavioral, psychological, educational, and skill-building interventions may be used to assist autistic people to learn daily life skills for living independently, as well as other social, communication, and language skills. Therapy also aims to reduce behaviors perceived as inappropriate and to build upon strengths. While medications have not been found to reduce autism's core features, they may be used for associated difficulties, such as irritability or inattention.

Non-pharmacological interventions

Certain interventions, such as intensive, sustained special education, remedial education programs, and behavior therapy, are considered beneficial early in life for autistic children to acquire self-care, social, and job skills. Available approaches include applied behavior analysis, developmental models, structured teaching, speech and language therapy, cognitive behavioral therapy, social skills therapy, and occupational therapy. These interventions may either target autistic features comprehensively or focus on a specific area of difficulty.

Applied behavior analysis

Applied behavior analysis (ABA) is a behavioral therapy that aims to teach autistic children certain social and other behaviors by rewarding them for desired behaviors and, in some particularly controversial cases, also by punishing them for undesired ones. Early, intensive ABA therapy is considered effective in language skills, adaptive functioning, and intellectual performance in preschool children. Another review reported the lack of adverse event monitoring, although such adverse effects are possibly common.

Interventions for early childhood may be based on different theoretical frameworks, such as ABA (with its structured and naturalistic approaches) and Developmental Social Pragmatic (DSP) models. Research indicates that in acquiring spoken language, autistic children with higher receptive language skills tend to make progress with fewer hours (2.5 to 20 per week) of a naturalistic approach, whereas those with lower receptive language skills tend to show more progress only with a greater intensity of intervention (25 hours per week) using discrete trial training, a structured form of ABA.

ABA has faced criticism. Sandoval-Norton et al. describe it as unethical and argue that it has unintended consequences, such as prompt dependency, susceptibility to psychological abuse, and overemphasis on compliance, which can create challenges in the transition to adulthood. Increasingly, ABA is also criticized for trying to reduce or eliminate autistic behaviors to make children appear more neurotypical, rather than respecting neurodiversity. A problem with unreported conflicts of interest in ABA research has been described, with potential effects on the quality of evidence. In response, some ABA advocates suggest that instead of discontinuing the therapy, efforts should focus on increasing protections and ethical compliance.

A related type of intervention is parent training models. These teach parents to implement various ABA and DSP techniques themselves. Several parent-mediated behavioral therapies target social communication difficulties, while their effect on restricted and repetitive behaviors (RRBs) is uncertain. Similarly, teacher-implemented interventions that combine naturalistic ABA with a developmental social pragmatic approach have been associated with effects on young children's social-communication behaviors, although there is limited evidence regarding effects on broader autistic characteristics.

Inclusion in education and the workplace

Inclusive education models strive to support autistic students in mainstream educational settings, moving away from segregated special education environments toward participation alongside their peers. Despite these efforts, autistic students can face significant barriers, sometimes leading to trauma or emotionally-based school non-attendance. This avoidance is often rooted in overwhelming sensory environments, social anxieties, communication breakdowns, bullying, or lack of adequate support and understanding, rather than defiance.

Central to successful inclusion is the application of frameworks like Universal Design for Learning (UDL), which proactively designs curricula and learning environments to be accessible and engaging for all students, including those with autism. UDL principles accommodate varied learning styles, sensory sensitivities, and communication preferences often present in autistic people.

The SPACE framework (sensory, predictability, acceptance, communication, empathy) developed by Doherty et al. primarily for healthcare settings offers a lens for identifying and addressing common environmental barriers that can contribute to distress and avoidance behaviors for autistic people. Accommodations may include providing quiet spaces as a retreat for people feeling overwhelmed. Autistic students may also need help initiating and maintaining social relationships with their peers if they wish to do so. Especially in higher education, some autistic students may need help with executive functioning, e.g., managing their own work, and the ability to initiate and complete tasks.

Transitioning to adulthood, autistic people often encounter substantial barriers to securing and maintaining meaningful employment, leading to high rates of unemployment and underemployment compared to the general population. Challenges can include navigating traditional interview processes, difficulties with unspoken social rules in the workplace, sensory sensitivities to office environments (e.g., lighting, noise), and needs for clear, direct communication and structured tasks. Effective workplace inclusion involves implementing reasonable adjustments such as flexible working hours or locations, providing noise-canceling headphones, staff training, and mentorship programs. Working from home can help to avoid overwhelming sensory or social situations, even if this means losing desirable social contact. Autism-friendly workplaces not only allow autistic employees to utilize their unique skills and perspectives but also benefit employers through increased innovation, problem-solving capabilities, and employee loyalty.

Pharmacological interventions

Autistic people may be prescribed medication to manage specific co-occurring conditions or behaviors, such as ADHD, anxiety, aggression, or self-injurious behaviors, particularly when non-pharmacological interventions alone have been insufficient. Medications are not routinely recommended for autism's core features, such as social and communication difficulties or restricted and repetitive behaviors.

More than half of autistic children in the United States are prescribed psychoactive drugs or anticonvulsants. Commonly used drug classes include antidepressants, stimulants, and antipsychotics. Among antipsychotics, risperidone and aripiprazole are the only medications approved by the U.S. Food and Drug Administration specifically for reducing irritability, aggression, and self-injurious behaviors in autistic people. These drugs can have significant side effects and responses to them may vary. The UK's National Health Service cautions against the overprescription of antipsychotics and recommends their use only for specific indications, at the lowest effective dose and for the shortest duration necessary.

Some research suggests that risperidone and aripiprazole may also reduce restricted and repetitive behaviors, such as hand-flapping or body-rocking. The evidence supporting this use has limitations, including study size and scope, alongside concerns about adverse effects. A meta-analysis found no significant efficacy of these antipsychotics or SSRI antidepressants in reducing these behaviors. Stimulant medications like methylphenidate may reduce inattention or hyperactivity in some autistic children, particularly when ADHD is also present. Experimental approaches such as MDMA-assisted psychotherapy are being explored for social anxiety in autistic adults.

Alternative medicine

Alternative therapies have been researched and implemented, and many have resulted in harm to autistic people. For example, chelation therapy is not recommended for autistic people, since the associated risks outweigh any potential benefits. In 2005, botched chelation therapy killed a five-year-old autistic child. Another alternative medicine practice with no evidence is CEASE therapy, a pseudoscientific mixture of homeopathy, supplements, and "vaccine detoxing". Medical authorities have condemned bleach-based approaches, such as chlorine dioxide solutions marketed as Miracle Mineral Solution, as dangerous and ineffective. There is also no evidence for the efficacy of hyperbaric oxygen therapy and its use is not recommended.

Although sometimes used for autistic people, no reliable evidence indicates a gluten- and casein-free diet as a standard intervention. Autistic children's preference for unconventional foods as well as gatrointestinal problems and lack of exercise can lead to reduction in bone cortical thickness, and this risk is greater in those on casein-free diets, as a consequence of the low intake of calcium and vitamin D.

A systematic review on interventions to address health outcomes among autistic adults found emerging evidence to support mindfulness-based interventions for improving mental health. This includes decreasing stress, anxiety, ruminating thoughts, anger, and aggression. An updated Cochrane review (2022) found evidence that music therapy likely supports the development of skills in social interaction, verbal communication, and nonverbal communication. Some studies on pet therapy have also shown effects, but further research is needed.

Causes

The exact causes of autism are unknown, with genetics likely being the largest contributing factor. It was long presumed a single cause at the genetic, cognitive, and neural levels underpinned the social and non-social features. Increasingly, autism is assumed to be a complex condition with distinct, often co-occurring, causes for its core aspects. It is unlikely that autism has a single cause; research has identified many factors as potential contributors, including genetics, prenatal and perinatal (shortly after birth) history, neuroanatomical anomalies, and environmental influences. It is possible to identify general factors, but difficult to determine specific ones. Research into causes is complex due to challenges in identifying distinct biological subgroups within the autistic population.

Genetics

Autism has a strong genetic basis, although the genetics of autism are complex and it is unclear whether autism is explained more by rare mutations with major effects, or by rare multi-gene interactions of common genetic variants. , it appeared that between 74% and 93% of autism likelihood is heritable. Numerous genes have been found, with most loci individually explaining less than 1% of autism cases and having only small effects. While these genetic variants are associated with a higher likelihood of being autistic, they do not individually determine whether someone will be autistic. Complexity arises due to interactions among multiple genes, the environment, and heritable epigenetic factors (which influence gene expression without changing DNA sequence).

Typically, autism is not traceable to a single-gene ( Mendelian) mutation or chromosome anomaly, and no associated genetic syndrome selectively causes autism. If autism is one characteristic of a broader medical condition, such as fragile X syndrome, it is referred to as syndromic autism, as opposed to non-syndromic or idiopathic autism, which is typically polygenic without a known cause. Syndromic autism is present in approximately 25% of autistic people. Research has suggested that autistic people with intellectual disability tend to have rarer, more impactful, genetic mutations than those found in people diagnosed solely with autism. A number of genetic syndromes causing intellectual disability may also be co-occurring with autism, including fragile X, Down, Prader–Willi, Angelman, Williams syndrome, branched-chain keto acid dehydrogenase kinase deficiency, and SYNGAP1-related intellectual disability.

Research suggests that autism is associated with genes that influence neural development and connectivity. These are involved in key neuronal processes such as protein synthesis, synaptic activity, cell adhesion, and the formation and remodeling of synapses, as well as the regulation of excitatory and inhibitory neurotransmission. Studies have identified lower expression of genes linked to the inhibitory neurotransmitter gamma-aminobutyric acid, alongside higher expression of genes associated with glial (e.g., astrocytes) and immune (e.g., microglia) cells, correlating with higher numbers of these cells in postmortem brain tissue. Genes associated with variation in the mTOR signaling pathway, which is involved in cell growth and survival, are also under investigation. Some hypotheses from evolutionary psychiatry propose that certain autism-associated genes may persist in the population due to their links to traits such as intelligence, systemising abilities, or innovation.

If parents have one autistic child, the chance of having a second autistic child ranges from 7% to 20%. If the autistic child is an identical twin, the other will be autistic 36% to 95% of the time. A fraternal twin is autistic up to 31% of the time. Although autism is highly heritable, many autistic people have only non-autistic family members. In some cases, this may be explained by de novo structural variations—such as deletions, duplications, or inversions—that arise spontaneously during meiosis and are not present in the parents' genomes. The likelihood of being autistic is greater with older fathers than with older mothers; two potential explanations are the known increase in the number of mutations in older sperm and the hypothesis that men marry later if they carry a genetic predisposition and show some signs of autism.

Early life

Certain factors during pregnancy and birth may increase the likelihood of autism, although no single factor is conclusive and study results are often inconsistent. These factors include advanced parental age, maternal health conditions (e.g., gestational diabetes, infections, inflammation), exposure to certain medications (e.g., valproate), and some environmental exposures like significant air pollution during pregnancy. While many environmental factors have been investigated, few have established links, and some prominent claims (e.g. vaccines or parenting styles) have been disproven.

Disproven vaccine hypothesis

Parents may first become aware of autistic characteristics in their child around the time of a routine vaccination. This has led to disproven theories blaming vaccine "overload", the vaccine preservative thiomersal, or the MMR vaccine for causing autism. In 1998, British physician and academic Andrew Wakefield led a fraudulent, litigation-funded study that suggested that the MMR vaccine may cause autism. His co-authors have since recanted the claims made in the study.

Two versions of the vaccine causation hypothesis were that autism results from brain damage caused by either the MMR vaccine itself, or by mercury used as a vaccine preservative. No convincing scientific evidence supports these claims. They are biologically implausible, and further evidence continues to refute them, including the observation that the rate of autism continues to climb despite elimination of thimerosal from most routine vaccines given to children from birth to 6 years of age.

A 2014 meta-analysis examined ten major studies on autism and vaccines involving 1.25 million children worldwide; it concluded that neither the vaccine preservative thimerosal ( mercury), nor the MMR vaccine, which has never contained thimerosal, lead to autism. Despite this, misplaced parental concern has led to lower rates of childhood immunizations, outbreaks of previously controlled childhood diseases in some countries, and the preventable deaths of several children.Vaccines and autism:
*
*
*
*
*

Neurocognitive theories

Various theoretical frameworks attempt to integrate underlying genetic and environmental causes with observed neurobiological findings and behavioral traits. For instance, the Intense World Theory proposes that a higher neural responsiveness in autism leads to more intense sensory perception, attention, memory, and emotional responses, shaping the person's experience. The Enhanced Perceptual Functioning model of autism posits that superior and more independent functioning of auditory and visual perception is the root cause of the specific pattern of cognitive, behavioral, and neural performance observed in autistic people. The model asserts the importance of perception, arguing it is more central to the autistic phenotype than social or higher-order cognitive processes.

Beyond models of causation and brain function, cognitive theories have been developed to explain patterns of information processing common in autistic people, to better understand the autistic phenotype. This includes theories suggesting a tendency to focus on details over broader context ( weak central coherence theory), and distinct cognitive styles related to analyzing systems versus empathizing with others ( empathising–systemising theory). While these cognitive accounts describe how autistic traits may manifest, they are generally viewed as explanations of the behavioral and cognitive consequences of the underlying neurobiological development rather than primary causes themselves.

Evolutionary hypotheses

Research exploring the evolutionary benefits of autism and associated genes has suggested that autistic people may have played a "unique role in technological spheres and understanding of natural systems" in the course of human development. It has been suggested that autism may have arisen as "a slight trade off for other traits that are seen as highly advantageous", providing "advantages in tool making and mechanical thinking", with speculation that the condition may "reveal itself to be the result of a balanced polymorphism, like sickle cell anemia, that is advantageous in a certain mixture of genes and disadvantageous in specific combinations". In 2011, a paper in ''Evolutionary Psychology'' proposed that autistic traits, including increased spatial intelligence, concentration and memory, could have been naturally selected to enable self-sufficient foraging in a more solitary environment. This is called the "Solitary Forager Hypothesis". A 2016 paper examines Asperger syndrome as "an alternative prosocial adaptive strategy" that may have developed as a result of the emergence of "collaborative morality" in the context of small-scale hunter-gathering, i.e., where "a positive social reputation for making a contribution to group wellbeing and survival" becomes more important than complex social understanding.

Some research suggests that recent human evolution may be a driving force in the rise of autism in human populations. Studies in evolutionary medicine indicate that as cultural evolution outpaces biological evolution, disorders linked to bodily dysfunction increase in prevalence due to lack of contact with pathogens and negative environmental conditions that once widely affected ancestral populations. Because natural selection favors reproduction over health and longevity, the lack of this impetus to adapt to certain harmful circumstances creates a tendency for genes in descendant populations to over-express themselves, which may contribute to mental conditions and autoimmune diseases, for example. Noting the failure to find specific alleles that reliably cause autism or rare mutations that account for more than 5% of the heritable variation in autism established by twin and adoption studies, research in evolutionary psychiatry has concluded that it is unlikely there is selection pressure for autism when considering that autistic people and their siblings tend to have fewer offspring on average. Instead autism may be better explained as a by-product of adaptive traits caused by antagonistic pleiotropy and by genes that are retained due to a fitness landscape with an asymmetric distribution.

Demographics

The World Health Organization estimates about 1 in 100 children were autistic between 2012 and 2021 with a trend of increasing prevalence over time. This may reflect an underestimate of prevalence in low- and middle-income countries. The number of people diagnosed has increased since the 1990s, and research suggests this may be due to increased recognition of autism.

Males are about three times more likely to be diagnosed with autism than females. Several theories about the higher prevalence in males have been investigated. Females, for example, are more likely to have associated cognitive disability, suggesting that less obvious forms of autism are likely being overlooked. Prevalence differences may also be a result of gender differences in expression of characteristics, with autistic women and girls showing less atypical behaviors and therefore being less likely to be diagnosed with autism. Most professionals believe that race, ethnicity, and socioeconomic background do not affect the occurrence of autism.

The Centers for Disease Control's Autism and Developmental Disabilities Monitoring Network reported that approximately 1 in 31 children in the United States is diagnosed with autism, based on data collected in 2022. For 2016 data, the estimate was 1 in 54, compared to 1 in 68 in 2010 and 1 in 150 in 2000. Diagnostic criteria for autism have changed significantly since the 1980s; for example, U.S. special-education autism classification was introduced in 1994.

In the UK, from 1998 to 2018, autism diagnoses increased by 787%. This is largely attributable to changes in diagnostic practices, referral patterns, availability of services, age at diagnosis, and public awareness, particularly among women, though unidentified environmental factors cannot be ruled out.

Research indicates that autistic people are significantly more likely to be LGBTQ than the general population. Autistic people are also significantly more likely to be non-theistic.

Etymology

In 1912, Swiss psychiatrist Paul Bleuler coined the German term ''Autismus'' in the context of describing a symptom of schizophrenia. Rendered in English as ''autism'', the term derives from the Greek word autos ("self") and suffix -ismos, denoting an action or state, and conveys the notion of "morbid self-absorption". In the 1920s, Grunya Sukhareva adopted the term to describe subjects who are autistic in the modern sense.

Society and culture

The autistic rights and neurodiversity movements argue autism should be accepted as a difference to be accommodated instead of cured,
although a minority of autistic people might still accept a cure. Social-science scholars study people with autism in hopes of learning more about "autism as a culture, transcultural comparisons ... and research on social movements". Events related to autism include World Autism Awareness Day, Autism Sunday, Autistic Pride Day, Autreat, and others.

Focused interests are commonly found in autistic people and can include activism. Environmental activist Greta Thunberg has spoken favorably about her autism diagnosis, saying that autism can be a source of life purpose, as well as the basis of careers, hobbies, and friendships.

Neurodiversity movement

Some autistic people and affiliated researchers have advocated a shift in attitudes toward the view that autism is a difference, rather than a disease that ought to be treated or cured. Critics have bemoaned the entrenchment of some of these groups' opinions, and that they speak to a select group of autistic people with limited difficulties.

The neurodiversity movement and the autism rights movement are social movements within the context of disability rights, emphasizing the concept of neurodiversity, which describes the autism spectrum as a result of healthy and valuable variations in the human brain rather than a disorder to be cured. The autism rights movement advocates including greater acceptance of autistic behaviors, therapies that focus on coping skills rather than imitating the behaviors of those without autism, and the recognition of the autistic community as a minority group. Autism rights or neurodiversity advocates believe that the autism spectrum is genetic and should be accepted as a healthy variation in the human genome.

These movements are not without detractors. A common argument against neurodiversity activists is that most have relatively low support needs, or are self-diagnosed, and do not represent the views of autistic people with higher support needs. Jacquiline den Houting explores this critique, determining that the voices of low-support needs autistics are "some of the most influential within the neurodiversity movement, although admittedly these voices are a minority within the advocacy community." Pier Jaarsma and Stellan Welin make the argument that only autistic people with lower support needs should be included under the neurodiversity banner, as autism with high support needs may rightfully be viewed as a disability. The concept of neurodiversity is contentious in autism advocacy and research groups and has led to infighting.

See also

* Outline of autism
* Animal model of autism
* Autism and memory
* Autism in popular culture
* Autistic art
* Controversies in autism
* Discrimination against autistic people
* Global perceptions of autism
* List of autistic fictional characters
* List of films about autism
* Mechanism of autism
* Violence and autism

Notes

References

Sources

*
*

External links

*
*

World Health Organization fact sheet on autism

{{Authority control

Autism spectrum disorders
Developmental psychology
Learning disabilities