Health and Medicine
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Bipolar disorder is characterized by bouts of extreme mood, with episodes of mania occurring alongside periods of depression. For the first time, researchers have now isolated the genetic factors responsible for the mania component, raising hopes of new treatments and more effective screening protocols.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.Affecting around two percent of the global population, bipolar disorder is a severe psychiatric condition that is notoriously difficult to treat. Part of the problem lies in the complexity of the disorder, which overlaps with numerous other mental health conditions, including major depressive disorder (MDD) and schizophrenia.
These similarities in symptomology make it difficult to reliably diagnose bipolar disorder, while also hindering efforts to study the condition. To overcome these obstacles, the authors of a new study examined the genomes of 576,327 people with MDD and 27,196 people with bipolar disorder.
This enabled them to subtract the genetic signals associated with MDD from those linked to bipolar, leaving behind only the genes responsible for mania. By utilizing such a large database of genetic information, the researchers were able to determine that mania accounts for 81.5 percent of the genetic variation in bipolar disorder, with depression causing the remaining 18.5 percent.
On top of this, the study authors identified 71 genetic variants linked to mania, including 18 that had never previously been associated with bipolar disorder. Many of these genes are also implicated in traits such as risky speeding behavior, reduced need for sleep, being a night-owl, heightened physical activity, and elevated mood – all of which helps to explain the intense bursts of energy and impulsivity that are typically associated with manic episodes.
At the same time, when compared to the depression component of bipolar disorder, the genes linked to mania showed a reduced correlation with traits such as alcohol, cannabis, and tobacco dependence, as well as risky sexual behavior. These findings suggest that the hypersexual behavior associated with bipolar disorder may not be driven by mania.
"By isolating the genetic architecture of mania, we have taken a crucial step towards understanding the core biology of bipolar disorder,” explained lead study author Dr Giuseppe Pierpaolo Merola in a statement. “This allows us to see what makes mania distinct, rather than viewing bipolar disorder simply as a mixture of mania, depression and psychosis, and opens new possibilities for more precise and personalized treatments."
For instance, many of the genes identified in the study alter the function of voltage-gated calcium channels, which regulate neural communication. Targeting this pathway may therefore offer a new and more effective therapeutic avenue for bipolar disorder.
“In the longer term, this could help clinicians recognize bipolar disorder earlier, reduce the long delays many patients face before receiving a diagnosis, and improve outcomes through more targeted treatment," said senior study author Professor Gerome Breen.
The study is published in the journal Biological Psychiatry.
