Previous studies looking at the genetics of bipolar disorder have focused primarily on people of European descent. The new study looked at more diverse groups. (Image credit: Design Cells via Getty Images)
Scientists have discovered about 300 “hot spots” in the human genome that may increase the likelihood of developing bipolar disorder.
In the largest study of its kind to date, an international research team conducted a detailed analysis of the DNA of nearly 3 million people, including more than 158,000 with bipolar disorder. The DNA samples were collected from people of European, East Asian, African and Latin American descent living in 27 countries.
In this genetic data set, the researchers identified 298 regions of the genome that contained genetic variations that could increase the risk of bipolar disorder. They also looked deeper into 36 specific genes associated with the disorder.
Of the 36 genes, 16 are classified as small-molecule targets that could be used as drugs to alter gene activity, first author Kevin Sean O'Connell, a researcher at the University of Oslo's Center for Precision Psychiatry, told Live Science in an email. “This suggests the possibility of developing new drugs, but further pharmacological research beyond the scope of this work is needed.” The new work was published Jan. 22 in the journal Nature.
Analysis of the genetic context of bipolar disorder
Bipolar disorder (BD) is a psychiatric condition characterized by extreme changes in mood and energy levels, including euphoric states, or manic episodes, and hopeless states, known as depressive episodes. People may also experience symptoms of mania and depression during mixed episodes. There are two main types of BD: bipolar I disorder — which involves prolonged cycles of depression and mania — and bipolar II disorder, which includes depression and “hypomania,” a less severe condition.
Bipolar disorder affects nearly 1 in 150 adults worldwide, but its biological basis is not fully understood. Evidence suggests that genetic factors play an important role, and certain genetic variations have previously been linked to the disorder. However, most previous studies have been conducted in people of European descent.
By combining people from different demographic groups in the study, scientists were able to identify genetic characteristics that are common to several groups, as well as unique traits that are found only in certain populations.
“We found a locus specific to East Asian ancestry that is associated with this disorder,” O'Connell said. “This particular variant is not present in people of European or African American ancestry. It will be interesting to see how this variant might impact risk.”
“However,” he added, “most variants show signs of different ancestors.”
The new study also quadrupled the number of genomic regions associated with BD compared to previous studies. However, what the previous studies and this new one have in common is that they provide “biological evidence” supporting lithium’s effectiveness as a treatment for BD, O’Connell noted. Two of the 36 genes the team identified are “lithium target genes,” he explained. Future studies could help uncover how these genes function and how they respond to the drug.
Lithium has long been used as a mood stabilizer to treat BD, but its mechanism of action is not fully understood, so this line of research may provide some clues. It is important to note that lithium can cause a number of side effects, so scientists are looking for new treatment options for the disorder.
There are some second-generation antipsychotics approved for bipolar disorder that bypass some of the problems associated with lithium, said Chaya Bhuvaneshwar, a psychiatrist, author, and medical director of the North Suffolk Mental Health Association, who was not involved in the study. “However, these antipsychotics also have their own problems,” including a potential increase in the risk of type 2 diabetes, she told Live Science in an email.
New research could be a stepping stone
Sourse: www.livescience.com
