Psychiatric genetics is a subfield of

behavioral neurogenetics Neurogenetics studies the role of genetics in the development and function of the nervous system. It considers neural characteristics as phenotypes (i.e. manifestations, measurable or not, of the genetic make-up of an individual), and is mainly ba ...

and

behavioral genetics Behavioural genetics, also referred to as behaviour genetics, is a field of scientific research that uses genetic methods to investigate the nature and origins of individual differences in behaviour. While the name "behavioural genetics" c ...

which studies the role of genetics in the development of

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 (such as

alcoholism Alcoholism is the continued drinking of alcohol despite it causing problems. Some definitions require evidence of dependence and withdrawal. Problematic use of alcohol has been mentioned in the earliest historical records. The World He ...

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 ...

bipolar disorder Bipolar disorder (BD), previously known as manic depression, is a mental disorder characterized by periods of Depression (mood), depression and periods of abnormally elevated Mood (psychology), mood that each last from days to weeks, and in ...

, and

autism 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 d ...

). The basic principle behind psychiatric genetics is that genetic polymorphisms (as indicated by linkage to e.g. a

single nucleotide polymorphism In genetics and bioinformatics, a single-nucleotide polymorphism (SNP ; plural SNPs ) is a germline substitution of a single nucleotide at a specific position in the genome. Although certain definitions require the substitution to be present in ...

) are part of the causation of

psychiatric disorders 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 ...

. Psychiatric genetics is a somewhat new name for the old question, "Are behavioral and psychological conditions and deviations inherited?". The goal of psychiatric genetics is to better understand the causes of psychiatric disorders, to use that knowledge to improve treatment methods, and possibly also to develop personalized treatments based on genetic profiles (see

pharmacogenomics Pharmacogenomics, often abbreviated "PGx," is the study of the role of the genome in drug response. Its name ('' pharmaco-'' + ''genomics'') reflects its combining of pharmacology and genomics. Pharmacogenomics analyzes how the genetic makeup o ...

). In other words, the goal is to transform parts of psychiatry into a

neuroscience Neuroscience is the scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions, and its disorders. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, ...

-based discipline. Recent advances in

molecular biology Molecular biology is a branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, biomolecular synthesis, modification, mechanisms, and interactio ...

allowed for the identification of hundreds of common and rare genetic variations that contribute to psychiatric disorders.

History

Research on psychiatric genetics began in the late nineteenth century with

Francis Galton Sir Francis Galton (; 16 February 1822 – 17 January 1911) was an English polymath and the originator of eugenics during the Victorian era; his ideas later became the basis of behavioural genetics. Galton produced over 340 papers and b ...

(a founder of psychiatric genetics) who was motivated by the work of

Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English Natural history#Before 1900, naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all speci ...

and his concept of desegregation. These methods of study later improved due to the development of more advanced clinical, epidemiological, and biometrical research tools. Better research tools were the precursor to the ability to perform valid family, twin, and adoption studies. Researchers learned that genes influence how these disorders manifest and that they tend to aggregate in families.

Heritability and genetics

Most psychiatric disorders are highly

heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cell (biology), cells or orga ...

; the estimated heritability for

, and

(80% or higher) is much higher than that of diseases like

breast cancer Breast cancer is a cancer that develops from breast tissue. Signs of breast cancer may include a Breast lump, lump in the breast, a change in breast shape, dimpling of the skin, Milk-rejection sign, milk rejection, fluid coming from the nipp ...

and

Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a neurodegenerative disease primarily of the central nervous system, affecting both motor system, motor and non-motor systems. Symptoms typically develop gradually and non-motor issues become ...

. Having a close family member affected by a mental illness is the largest known risk factor, to date. However,

linkage analysis Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction. Two genetic markers that are physically near to each other are unlikely to be separ ...

and

genome-wide association studies In genomics, a genome-wide association study (GWA study, or GWAS), is an observational study of a genome-wide set of genetic variants in different individuals to see if any variant is associated with a trait. GWA studies typically focus on assoc ...

have found few reproducible

risk factors In epidemiology, a risk factor or determinant is a variable associated with an increased risk of disease or infection. Due to a lack of harmonization across disciplines, determinant, in its more widely accepted scientific meaning, is often ...

Heterogeneity Homogeneity and heterogeneity are concepts relating to the uniformity of a substance, process or image. A homogeneous feature is uniform in composition or character (i.e., color, shape, size, weight, height, distribution, texture, language, i ...

is an important factor to consider when dealing with genetics. Two types of heterogeneity have been identified in association with psychiatric genetics: causal and clinical. Causal heterogeneity refers to a situation in which two or more causes can independently induce the same clinical syndrome. Clinical heterogeneity refers to when a single cause can lead to more than one clinical syndrome. Tsuang, M., Taylor, L., Faraone, S. (2003). "Psychiatric genetics: future and prospects". In Leboyer, M, Bellivier, F. Psychiatric genetics: methods and reviews. Humana Press. pp. 251–265. Several genetic risk factors have been found with the

endophenotype In genetic epidemiology, endophenotype (or intermediate phenotype) is a term used to separate behavioral symptoms into more stable phenotypes with a clear genetic connection. By seeing the EP notion as a special case of a larger collection of mul ...

s of psychiatric disorders, rather than with the diagnoses themselves. That is, the risk factors are associated with particular symptoms, not with the overall diagnosis. In psychiatry,

s are a way of objectively measuring certain internal processes in a reliable way that is often lacking the diseases with which they are associated. They lie in the space between genes and disease process and allow for some understanding of the biology of psychiatric diseases. A systematic comparative analysis of shared and unique genetic factors highlighted key gene sets and molecular processes underlying six major neuropsychiatric disorders:

attention deficit hyperactivity disorder 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 con ...

anxiety disorders Anxiety disorders are a group of mental disorders characterized by significant and uncontrollable feelings of anxiety and fear such that a person's social, occupational, and personal functions are significantly impaired. Anxiety may cause phys ...

, autistic spectrum disorders,

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

. This may ultimately translate into improved diagnosis and treatment of these debilitating disorders.

Methodology

Linkage, association, and

microarray A microarray is a multiplex (assay), multiplex lab-on-a-chip. Its purpose is to simultaneously detect the expression of thousands of biological interactions. It is a two-dimensional array on a Substrate (materials science), solid substrate—usu ...

studies generate raw material for findings in psychiatric genetics. Copy number variants have also been associated with psychiatric conditions.Bourgeron, T., Giros, B.,(2003). " Genetic Markers in Psychiatric Genetics". In Leboyer, M, Bellivier, F. Psychiatric genetics: methods and reviews. Humana Press. pp. 63–98. Genetic Linkage studies attempt to find a correlation between the diagnosis and inheritance of certain alleles within families who have two or more ill relatives. An analysis of a linkage study uses a wide chromosomal region, whereas a genetic association study endeavors to identify a specific DNA polymorphism, which can be a deletion, inversion, or repletion of a sequence. Case-control association studies can be used as an exploratory tool for narrowing the area of interest after preliminary mapping of a gene by a linkage study.Bellivier, F. (2003). "Genetic association studies: definition of cases and controls". In Leboyer, M, Bellivier, F. Psychiatric genetics: methods and reviews. Humana Press. pp. 127–141.

Predictive genetic testing

One hope for future

genetic testing Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...

is the ability to test for presymptomatic or prenatal illnesses. This information has the potential to improve the lives of those affected with certain illnesses, specifically those like

. If possible to test for schizophrenia before the symptoms develop, proactive interventions could be developed, or even preventative treatments. In one study, 100% of patients with bipolar disorder indicated that they would probably take a genetic test to determine they were carrying a gene associated with the disorder, if such a test existed.

Ethical issues

studied both desirable and undesirable behavioral and mental properties to better examine the world of genetics. His research led to his proposal of a eugenic program of birth control. His goal was to decrease the frequency of the less desirable traits that occurred throughout the population. His ideas were pursued by psychiatrists in many countries such as the United States, Germany and Scandinavia. Genotyping and its implications are still seen as ethically controversial by many people. The ELSI (Ethical, Legal, and Social Initiative), which is part of the

Human Genome Project The Human Genome Project (HGP) was an international scientific research project with the goal of determining the base pairs that make up human DNA, and of identifying, mapping and sequencing all of the genes of the human genome from both a ...

, was created with the aim of "foster ngbasic and applied research on the ethical, legal and social implications of genetic and genomic research for individuals, families and communities.".

References

External links

Behavioral Genetics Association

IBANGS

International Society of Psychiatric Genetics
{{Psychiatry Causes of mental disorders Biology of bipolar disorder Biological psychiatry Behavioural genetics Medical genetics

History

Heritability and genetics

Methodology

Predictive genetic testing

Ethical issues

See also

References

External links