People who have disrupted sleep cycles or less variation in their activity levels around the clock may be more likely to have depression, bipolar disorders and other mental health issues. Past research has found that people with a circadian rhythm, or biological clock, that’s out of step with their daily routines, like split shift or night shift workers, can have an increased risk of emotional, behavioral and psychological problems. According to Reuters, the current study examined 24-hour activity levels for 91,015 participants who agreed to wear accelerometers on their wrists for one week in 2013-2014 and completed mental health surveys a few years later. Researchers focused on so-called relative amplitude, or how much people’s activity levels varied between their busiest and most restful portions of a 24-hour cycle. Then, researchers sorted participants into five groups, based on the amplitude results, and found that each one-quintile reduction in relative amplitude was associated with 6 percent higher lifetime risk of major depressive disorder, an 11 percent greater risk of bipolar disorder and 2 percent higher likelihood of mood instability. Dr. Raymond Lam, a psychiatry researcher at the University of British Columbia in Vancouver, Canada, who wasn’t involved in the study, said: “Regulating circadian rhythms is an important part of maintaining optimal mood and cognitive functioning.” “That includes having a regular sleep schedule (sleeping and waking at about the same times), keeping active and exercising (which helps to regulate rhythms), avoiding late night light exposure (such as from mobile devices), and avoiding or addressing the circadian disruptions from shift work,” Lam added. Dr. Teodor Postolache, a psychiatry researcher at the University of Maryland School of Medicine in Baltimore who wasn’t involved in the study as well, said: “Even though the study doesn’t show whether sleep problems cause mood disorders or whether mental health issues lead to sleep difficulties, the results still suggest people may feel better when they try to keep their routines in sync with their circadian rhythm.”