Scientists at Massachusetts General Hospital (MGH) and the Psychiatric Genomics Consortium have discovered that many distinct psychiatric diseases share a common genetic basis. Published in Cell, the study carried out genome-wide meta-analysis to identify more than 100 genetic variants that play a role in determining risk levels for different mental health conditions.

The eight most common psychiatric disorders worldwide are; anorexia nervosa, attention-deficit/hyperactivity disorder, autism spectrum disorder, bipolar disorder, major depression, obsessive-compulsive disorder, schizophrenia, and Tourette syndrome. The genetics underlying these disorders is not fully understood, and it’s suggested that several genes together could influence the development of them – known as pleiotropy. More than 25% of the population is affected with a psychiatric disorder every year.

Genetic data from 494,162 healthy control subjects and 232,965 people diagnosed with at least one of the eight common psychiatric disorders was analysed using WGS to identify 109 gene variants that could increase the risk of developing a psychiatric disorder. The 109 gene variants were associated with at least two psychiatric disorders. Of these, 23 variants had pleiotropic effects on four or more disorders, and 11 variants had antagonistic effects on multiple disorders.

Some variants were shared among certain disorders and were divided into three groups of genetically-related conditions: early-onset neurodevelopmental disorders (autism spectrum disorder, ADHD and Tourette syndrome); mood and psychotic disorders (major depression, bipolar disorder and schizophrenia); and compulsive behaviour disorders (anorexia nervosa, obsessive-compulsive disorder and, to a lesser extent, Tourette syndrome).

The research also showed that these genes play an important role in brain development and are more expressed during the second trimester of pregnancy.

Understanding the underlying genetics of these disorders can provide clues to biological pathways and could inform how we classify and diagnose mental health conditions. They could elucidate potential targets in new drug development and could benefit a number of patients who’s genetics predispose them to these conditions.