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A new study finds links between sleeping patterns, circadian rhythms, bipolar disorder and specific phenotypes. Researchers from the University of California, Los Angeles (UCLA) and the University of Texas Southwestern Medical Centre have determined that these links can help in the development of new strategies to prevent and treat bipolar disorder.

"We were able to identify 13 sleep and activity measures, most of which are inherited, that correlated with whether an individual had bipolar disorder,” Joseph Takahashi, chairman of Neuroscience and investigator in Howard Hughes Medical Institute (HHMI) at UT Southwestern, said in a news release. “In addition, we were able to trace some of these traits to a specific chromosome."

Although bipolar disorder has both environmental and genetic causes, researchers have suspected that circadian rhythms, the body's natural sleep, wake and activity cycle, can precede mood shifts and play a role in the disorder. The team found that participants with bipolar disorder awoke later and slept longer. These individuals also displayed lower activity levels while awake and had greater variations in sleep and wake cycles.

The researchers studied 558 members of 26 Costa Rican and Colombian families where 136 of them have bipolar disorder. Thirteen heritable phenotypes which are associated with bipolar disorder included mean of awake duration, amplitude, Hill acrophase, interdaily stability, interdaily variability, median activity, relative amplitude, mean length of sleep bouts during the sleep period, mean number of sleep bouts during awake period, time of sleep offset, time of sleep onset, mean total minutes scored awake and WASO (total minutes in awake bouts after sleep onset).

Bipolar disorder affects more than 30 million people worldwide. Headspace Australia said that 1.8 percent of males and 1.7 percent of females live with bipolar disorder in the country. Additionally, 3.2 percent of Australian men and 3.6 percent of Australian women, aged 16 to 24 years, had the bipolar disorder in their lifetime.

Nelson Freimer, chair of Psychiatry and director of the Centre for Neurobehavioral Genetics at UCLA, said that the study represents a key step in identifying the genetic roots of the disorder. Freimer believes that these findings can provide the foundation for new approaches to treating and preventing bipolar disorder.