Researchers have identified a variety of inherited traits related to the sleep, wake and activity cycles of people with severe bipolar disorder, according to a novel study at the University of Texas (UT) Southwestern Medical Center and the University of California, Los Angeles (UCLA).
The researchers were able to link these traits to specific chromosomes, providing important clues to the genetic nature of the disorder as well as potential new pathways for prevention and treatment.
“We were able to identify 13 sleep and activity measures, most of which are inherited, that correlated with whether an individual had bipolar disorder. In addition, we were able to trace some of these traits to a specific chromosome,” said Dr. Joseph Takahashi, chairman of Neuroscience and a Howard Hughes Medical Institute (HHMI) Investigator at UT Southwestern.
“This study represents a key step in identifying the genetic roots of this disorder and, in turn, providing targets for new approaches to preventing and treating bipolar disorder,” said Dr. Nelson Freimer, who directs the Center for Neurobehavioral Genetics at UCLA.
Bipolar disorder is characterized by dramatic mood shifts in which the person is overly excited, extremely sad or depressed, or a mixed state of both, which may involve irritable or explosive behavior, according to the National Institute of Mental Health.
Researchers have long suspected that disruption in normal daily circadian rhythms, including the sleep and wake cycles, can precede these mood shifts.
Researchers discovered that patients with bipolar disorder awoke later and slept longer, were awake fewer minutes overall and had greater variations in sleep and wake cycles. They also found that individuals with bipolar disorder had lower activity levels while awake and were active for shorter periods than those without the disorder.
The study, involving more than 500 members of 26 families from Costa Rica and Colombia, is the first large-scale study of sleep and activity traits in bipolar-affected individuals and their relatives and the first genetic study of such a comprehensive set of sleep and circadian measures in any human study.
The findings are published in the journal Proceedings of the National Academy of Sciences.
Source: UT Southwestern Medical Center