WASHINGTON (Dispatches) -- A genetic study of 840,000 people found that shifting sleep time earlier by just an hour decreases risk of major depression by 23 percent, reports a study of 840,000 people by researchers at University of Colorado Boulder and the Broad Institute of MIT and Harvard.
The researchers say that there is a relationship between sleep timing and mood. The study
represents some of the strongest evidence yet that chronotype -- a person’s propensity to sleep at a certain time -- influences depression risk.
Previous observational studies have shown that night owls are as much as twice as likely to suffer from depression as early risers, regardless of how long they sleep. But because mood disorders themselves can disrupt sleep patterns, researchers have had a hard time deciphering what causes what.
Other studies have had small sample sizes, relied on questionnaires from a single time point, or didn’t account for environmental factors which can influence both sleep timing and mood, potentially confounding results.
Each one-hour earlier sleep midpoint (halfway between bedtime and wake time) corresponded with a 23% lower risk of major depressive disorder.
This suggests that if someone who normally goes to bed at 1 a.m. goes to bed at midnight instead and sleeps the same duration, they could cut their risk by 23%; if they go to bed at 11 p.m., they could cut it by about 40%.