In a study forthcoming in the journal Biological Psychiatry, researchers from the University of New South Wales and Australia's Black Dog Institute measured brain activity in 47 young adults thought to have a genetic risk for bipolar disorder -- identified by having a close relative with the condition -- and 49 controls. The subjects' brains were scanned using MRI technology as they were shown pictures of human faces with fearful, happy or neutral expressions.
"We found that the young people who had a parent or sibling with bipolar disorder had reduced brain responses to emotive faces, particularly a fearful face. This is an extremely promising breakthrough," study leader and UNSW researcher Philip Mitchell said in a statement Monday.
The difference in brain activity between subjects at risk for bipolar disorder and controls centered on the inferior frontal gyrus, a part of the frontal lobe thought to be involved in regulating emotions.
“We know that bipolar is primarily a biological illness with a strong genetic influence but triggers are yet to be understood. Being able to identify young people at risk will enable implementation of early intervention programs, giving them the best chance for a long and happy life,” Mitchell says.
According to the National Institute of Mental Health, about 2.6 percent of the adult population of the U.S. has bipolar disorder, with a strong majority of those cases -- nearly 83 percent -- classified as severe. Bipolar disorder tends to develop later in life; on average, a person starts showing signs of the disorder around age 25.
Less than half of people with bipolar disorder are receiving any kind of treatment through the health care system in the U.S. Only around 19 percent of people with bipolar disorder are receiving what the NIMH considers “minimally adequate treatment.”
People with bipolar disorder can experience different degrees of the condition. Some have very high energy episodes of mania contrasting with major depressive episodes. Others experience occasional high energy and impulsiveness that don't quite meet the definition of full-blown mania. Still others can have a mild form of bipolar disorder called cyclothymia, which involves less severe mood swings.
There is much evidence to suggest that bipolar disorder has a genetic component, though it is still unclear which gene or genes may be involved. Another study published in Biological Psychiatry in October, from a group of King's College London scientists, zeroed in on a gene called PBRM1. This gene codes for a protein involved in a process called chromatin remodeling, which can expose certain parts of the genome to be transcribed and thereby influence how genes are expressed. Chromatin remodeling is a major factor in epigenetics -- how environmental conditions can influence the expression of genes.
SOURCE: Roberts et al. “Reduced Inferior Gyrus Activation During Response Inhibition to Emotional Stimuli in Youth at High Risk of Bipolar Disorder.” Biological Psychiatry in press.