New study doubles known bipolar genes

03 May 2019

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The largest ever genome-wide study of bipolar has found important new genetic links.

Bipolar is a psychiatric condition characterised by extreme mood swings between mania and depression, and it affects around 40 million people around the world. Whilst we know bipolar is inherited genetically, and we’re aware of a few genes linked to it, we still don’t really know what causes it.

That’s the basis for a new genome-wide association study published in Nature Genetics by an international group called the Psychiatric Genomics Consortium. They’re trying to identify the genetic underpinnings of major psychiatric conditions, and in this case bipolar.

Lead author Eli Stahl said that the researchers analysed genome data from over 50,000 subjects in 14 different countries. “This is by far the largest study of its kind in bipolar disorder. There are over 250 collaborators involved.”

The huge sample meant that they could connect the dots to find 30 genetic associations with bipolar - including 20 that are brand new to science. This has doubled the number of known associations for the disorder.

Most of these genes play roles in the brain, specifically in neurotransmitter signalling - the chemicals neurons use to communicate with each other.

Each of the new genetic associations could be a target for treatment. This means synthesizing new drugs, or repurposing medications normally used for other psychiatric disorders. 

Simon Kitchen, Chief Executive of Bipolar UK, is glad to see so many new links discovered. “It holds open the hope that we’ll be able to develop more personalised treatments for people living with bipolar.”

Researchers went on to calculate a risk score for each genome: a measure of each one’s genetic predisposition to bipolar, or to different bipolar symptoms. Then, they compared these to similar risk scores for other psychiatric conditions.

What they found reinforced old hypotheses around links between the major disorders. Bipolar patients on the whole had a higher risk than healthy patients for schizophrenia and depression.

The results also distinguished between the two types of bipolar: bipolar 1 and bipolar 2. Bipolar 1 was correlated with schizophrenia, and bipolar 2 with major depression.

Stahl described the findings as “adding to the picture we have of bipolar as an intermediate between schizophrenia and major depression.”

Knowing this, the team plan to explore further connections between genes and specific symptoms.

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