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Scientists find that 13 inherited characteristics are related to severe bipolar disorder. It includes problems that patients have with sleeping, waking or "cycle activities", according to scienceworldreport.

Both genetic and environmental factors can lead to the bipolar disorder that cause huge shifts in moods, reports the National Institute of Mental Health. Earlier research shows that disruptions in normal circadian rhythms, which includes sleep as well as wake cycles, are also linked to shifts in the mood.

"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 and holds the Maggie Gilbert Chair of Psychiatry at UCLA, in a news release.

More than 500 members of 26 families from Costa Rica and Colombia were studied, many of them with an excessive bipolar disorder. Scientists found 13 sleep and activity measures closely linked with the behavioral disorder. A few were identified with a particular chromosome.

The 13 endophenotypes, or biological or behavioral markers that are located more commonly in patients of the disorder include: "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)".

The study is published in the Proceedings of the National Academy of Sciences (PNAS).