Study Identifies 30 Genes Linked to Bipolar Disorder

The research, which brought together organisations from around the world, has identified 30 areas where variations in genetic code can increase the risk of developing the mental health condition, which causes extreme mood swings.  Identifying these areas could enable the development of more specialised medications.

The global study, conducted by the Bipolar Disorder Workgroup of the Psychiatric Genomics Consortium, compared genetic variations in blood samples from more than 29,000 people with bipolar disorder and 160,000 people who do not have the condition.  Researchers analysed hundreds of thousands of genetic markers.  They compared the variations in these markers between people with and without bipolar disorder, which revealed 30 areas of the DNA sequence (genes) where there are differences.

Professor Lisa Jones, principal investigator at the Bipolar Disorder Research Network (BDRN), a collaboration between the University of Worcester and Cardiff University, which led the research, said: “We have very little understanding of what causes people to have severe mental illness.  These findings are important because understanding the underlying genetic causes of bipolar disorder helps us to understand more about the biology of what’s happening in the brain to cause the illness. 

“We ultimately hope this will lead to the development of better treatments and more targeted treatments that don’t have such wide ranging side effects and will hopefully result in better outcomes for people affected.” 

This is the culmination of more than 10 years of research, involving researchers from more than 200 institutions all over the world. 

Professor Jones said that, although studies have looked at genetic variants before, they have not done so on this scale.  Previous studies had always concluded that the sample sizes needed to be greater to find the genetic variations.

“We need a large sample size because each person’s experience of bipolar disorder is unique,” said Professor Jones, who is a Professor of Psychological Medicine at the University of Worcester and Principal Investigator in the University's Mood Disorders Research Group. 

“Each of these genetic variants will increase somebody’s risk for bipolar disorder by just a very small amount and because it’s very small differences that we’re looking at we need very big sample sizes to find them.  Bipolar disorder is a complex disorder; we know there are genetic and non-genetic factors involved and it’s like trying to put together parts of a very complex jigsaw. We’re interested in genetics because the main known risk factor for having bipolar disorder is having a family history of it.”

Dr Arianna Di Florio, Clinical Senior Lecturer at Cardiff University’s MRC Centre for Neuropsychiatric Genetics and Genomics, added: “Our analyses pointed to genes relevant to the nervous, immune and metabolic systems.

“We also found differences in the genetic make-up between individuals with bipolar I disorder, who have a history of severe manic episodes, and those with bipolar II disorder, who don’t experience such severe episodes.

“This was a truly global effort, which would not have been possible without so many people giving up their time to take part in the research, so on behalf of the workgroup I would like to thank all those who contributed to this work.”

These findings pave the way for more intensive studies of the genetic variants identified and their relationship with specific sets of bipolar disorder symptoms.

The paper, Genome-wide association study identifies 30 loci associated with Bipolar Disorder, is published in Nature Genetics.