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Psychiatric disorders share common genetic causes

Psychiatric disorders like schizophrenia and bipolar disorder share similar genetic causes, and probably have important similarities at a molecular level, a new study has found.

The study, published yesterday in the journal Science, concludes that this could have implications for how these disorders are treated.

Professor Nick Wood, Director of Neurosciences at the UCLH/UCL BRC, and UCL-UK DRI researchers Dr Rita Guerreiro and Dr Jose Bras, helped oversee the work and analyse the data.

Broad Institute of MIT and Harvard University in the US led the work, which involved researchers from over 600 institutions.

Researchers looked for similarities in the genes responsible for various psychiatric conditions.

They found that the genetic overlap between attention-deficit/hyperactivity disorder (ADHD), bipolar disorder, major depressive disorder and schizophrenia was greater than expected.

A strong overlap was also found between anorexia nervosa and obsessive-compulsive disorder (OCD), as well as between OCD and Tourette syndrome.

Neurological disorders, such as Parkinson’s and Alzheimer’s, appeared to be more genetically distinct, both from one another and from other psychiatric disorders.

The neurological disorder migraine however was found to share genetic overlap with ADHD, major depressive disorder and Tourette syndrome.

According to the researchers, the high degree of genetic correlation among psychiatric disorders suggests that current disease categories do not accurately reflect the underlying biology of the disorders.

Co-senior study author Professor Ben Neale, institute member at Broad Institute, said: “The tradition of drawing these sharp lines when patients are diagnosed probably doesn’t follow the reality, where mechanisms in the brain might cause overlapping symptoms.”

As a hypothetical example given by researchers, a single mechanism regulating concentration could drive both inattentive behaviour in ADHD and diminished executive function in schizophrenia.

Commenting on the study and its implications for treatment, Professor Wood said: “This study emphasises the power and potential of very large scale collaborative efforts. By sharing and comparing data across multiple brain disorders our understanding of how the various disorders develop can be increased. This opens the door to new thinking on how best to approach novel treatments.”

The research also looked at the relationship between psychiatric and neurological disorders and 17 physical or cognitive measures, such as years of education. It found that higher levels of education are linked to an increased risk of anorexia, autism, bipolar disorder and OCD.

Neurological disorders, however, particularly Alzheimer’s and stroke, followed the opposite pattern. Higher levels of education were associated with a lower risk of developing these disorders.