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Common mental disorders share a genetic link

4 March 2013
Appeared in BioNews 695

Five of the most common psychiatric disorders share genetic risk factors, an international study published in the Lancet has found. These disorders include; autism, attention deficit hyperactivity disorder (ADHD), clinical depression, bipolar disorder and schizophrenia.

'These disorders that we thought of as quite different may not have such sharp boundaries', said one of the lead researchers, Dr Jordan Smoller of Massachusetts General Hospital, USA.

In the largest genetic study of mental illness to date, researchers compared the genomes of 33,000 people with one of five common psychiatric disorders to nearly 28,000 unaffected controls. All participants were of European ancestry. Genetic variations called single nucleotide polymorphisms (SNPs) identified in four regions of the genome were significantly associated with the psychiatric disorders. Two of these regions were involved in regulating the flow of calcium in nerve cells – a process that regulates brain activity.

These findings hint at a possible shared mechanism in the development of several mental disorders. Marjorie Wallace, chief executive of mental health charity SANE, told the BBC 'the findings highlight the need to understand the genetic and biological factors of these life-changing conditions, in order that more effective treatments and therapies may be found'.

The identification of shared genetic risk factors for different psychiatric disorders may help explain previously observed connections between certain disorders. For instance, those in families with a history of bipolar disorder are suggested to have an increased risk of schizophrenia (reported in BioNews 491).

Although the SNPs identified in this study cannot predict or diagnose the mental disorders investigated, as their effects are too small, the findings have fuelled the hope that a better understanding of the genetic contributions to these conditions could impact diagnosis in the future. Currently, the diagnosis of psychiatric disorders is based entirely on symptoms.

Professor Nick Craddock from Cardiff University, who was involved in the study, told the BBC: 'It signals the opening of a potential new era for psychiatry and mental illness. This is a scientific method that helps understand what is going wrong in the brain'.

5 Most Common Mental Illnesses Share the Same Genes
National Institute of Mental Health (press release) |  28 March 2013
Five 'mental disorders' may have genetic links
NHS Choices |  28 March 2013
Five psychiatric disorders 'linked'
BBC News |  28 March 2013
Identification of risk loci with shared effects on five major psychiatric disorders: a genome-wide analysis
The Lancet |  28 March 2013
Most Common Psychiatric Disorders Share Genetic Roots
Time |  28 March 2013
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Comment ( - 17/04/2013)
The same issue of BioNews (#695: 04/03/2013) which reported a genetic basis to bi-polar disorder also included a link to a Feb 14/13 Sunday Express news story, "IVF clinics reject donor eggs from bipolar women" in which Robert Winston disputes any genetic connection: “This is not a genetic condition; there is no evidence that it is an inherited condition. In fact, all the evidence points to the fact that it probably isn’t."
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