Disrupted sleep cycles may cause depression
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, a UK study suggests.
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. 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.
They scored circadian amplitude from zero to 1, with higher values reflecting a clearer distinction between the least and most active parts of the day and lower values indicating too little daytime activity, too much nighttime activity, or both.
On average, participants had a relative amplitude level of 0.87, which is similar to what would be expected in a healthy population, the study found.
When researchers sorted participants into five groups, or quintiles, based on the amplitude results, they found that each one- quintile reduction in relative amplitude was associated with 6 per cent higher lifetime risk of major depressive disorder, an 11 per cent greater risk of bipolar disorder and 2 per cent higher likelihood of mood instability.
“Regulating circadian rhythms is an important part of maintaining optimal mood and cognitive functioning,” said Dr. Raymond Lam, a psychiatry researcher at the University of British Columbia in Vancouver, Canada, who wasn’t involved in the study.
“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 said by email. One limitation of the study, however, is that it measured activity levels at one point in time and mental health conditions were assessed at a different time. It wasn’t a controlled experiment designed to prove whether or how variation in sleep cycles directly might cause psychological problems.