Psychiatric genetics is a subfield of behavioral neurogenetics 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 or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. Such features may be persistent, relapsing and remitti ...

s (such as

alcoholism Alcoholism is, broadly, any drinking of alcohol that results in significant mental or physical health problems. Because there is disagreement on the definition of the word ''alcoholism'', it is not a recognized diagnostic entity. Predomi ...

schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social w ...

bipolar disorder Bipolar disorder, 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 last from days to weeks each. If the elevat ...

, and

autism The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental condition (or conditions) characterized by difficulti ...

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

single nucleotide polymorphism In genetics, 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 a sufficiently larg ...

) are part of the causation of

psychiatric disorders A mental disorder, also referred to as a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. Such features may be persistent, relapsing and remitt ...

. 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 Causes, or causality, is the relationship between one event and another. It may also refer to: * Causes (band), an indie band based in the Netherlands * Causes (company) Causes.com is a civic-technology app and website that enables users to orga ...

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 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 of an individual affects the ...

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

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

-based discipline. Recent advances in

molecular biology Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and phys ...

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, FRS FRAI (; 16 February 1822 – 17 January 1911), was an English Victorian era polymath: a statistician, sociologist, psychologist, Anthropology, anthropologist, tropical Exploration, explorer, geographer, Inventio ...

(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 naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...

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 traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic informa ...

; the estimated heritability for

, and

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

breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or ...

and

Parkinson disease Parkinson may refer to: * Parkinson (surname) * ''Parkinson'' (TV series), British chat show, presented by Sir Michael Parkinson * Parkinson, Queensland, suburb of Brisbane, Australia *The Parkinsons (fl. early 20th century), American father-and-so ...

. 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 sepa ...

and

genome-wide association studies In genomics, a genome-wide association study (GWA study, or GWAS), also known as whole genome association study (WGA study, or WGAS), is an observational study of a genome-wide set of genetic variants in different individuals to see if any varian ...

have found few reproducible risk factors.

Heterogeneity Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the uniformity of a substance or organism. A material or image that is homogeneous is uniform in composition or character (i.e. color, shape, siz ...

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. The concept was coined by Bernard John and Kenneth R. Lewis in a 1966 pap ...

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 excessive amounts of inattention, hyperactivity, and impulsivity that are pervasive, impairing in multiple contexts, and otherwise age-inap ...

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

autistic spectrum disorders The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental condition (or conditions) characterized by difficulti ...

major depressive disorder Major depressive disorder (MDD), also known as clinical depression, is a mental disorder characterized by at least two weeks of pervasive low mood, low self-esteem, and loss of interest or pleasure in normally enjoyable activities. Intro ...

, and

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

Methodology

Linkage, association, and

microarray A microarray is a multiplex lab-on-a-chip. Its purpose is to simultaneously detect the expression of thousands of genes from a sample (e.g. from a tissue). It is a two-dimensional array on a solid substrate—usually a glass slide or silicon ...

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 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 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 ph ...

(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 ...

, 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