Early birds don’t just get the worm, they reduce their risk of suffering major depression by a whopping 23 per cent, according to a new study.
The research, published in JAMA Psychiatry, found compelling evidence that chronotype — a person’s tendency to go to sleep at a certain time — plays a powerful role in the risk of depression. The findings present an opportunity to shore up mental health in the post-pandemic era as vast amounts of people leave the relative safety of their homes and return to the real world.
“We have known for some time that there is a relationship between sleep timing and mood, but a question we often hear from clinicians is: How much earlier do we need to shift people to see a benefit?” said Celine Vetter, senior author of the study and an assistant professor of integrative physiology at University of Colorado Boulder. “We found that even one-hour earlier sleep timing is associated with significantly lower risk of depression.”
While previous research has found staying up late can almost double the risk of depression compared to rising early — regardless of time spent asleep — mood disorders and other variables have made it difficult to discern cause from effect. Other relevant studies have suffered from small sample sizes or have not adequately accounted for environmental factors that may impact results, the study said.
To paint a clearer picture of the protective effect of shifting sleeping patterns, researchers pored over data from 23 and Me, a DNA testing company, and the UK Biobank, a large-scale health database containing the in-depth genetic and medical information of half a million people. They used “Mendelian randomization” a process that helps determine cause and effect by leveraging genetic associations.
“Our genetics are set at birth so some of the biases that affect other kinds of epidemiological research tend not to affect genetic studies,” said Iyas Daghlas, the study’s lead author and a recent graduate from Harvard Medical School.
There are more than 340 common genetic variants that influence a person’s chronotype, including PER2 — better known as the clock gene, according to the study. All told, genetics account for 12-42 per cent of an individual’s typical sleep pattern. The team analyzed the role these genetic variants (which were initially “de-identified” for the purpose of the study) played in a pool of 850,000 individuals, incorporating data from 85,000 participants who wore sleep trackers for a week and 250,000 people who filled out questionnaires on sleep preference.
In the largest sample group, roughly one-third of participants identified as early risers, nine per cent were night owls and the rest fell somewhere in the middle. The group’s average sleep midpoint was 3 a.m. — meaning they went to sleep at 11 p.m. and rose at 6 a.m. Researchers then compared these findings to a different sample that included genetic information along with anonymized medical and prescription records and surveys about depressive disorder.
They determined that people possessing genetic variants that predisposed them to be early risers also experienced a reduced risk of depression. Shifting an individual’s sleep midpoint one hour earlier carried a 23 per cent lower risk of major depressive disorder. Another hour earlier cut the risk by 40 per cent. While it isn’t clear if this protective benefit extends to people who are already early risers, it proved helpful for the vast amount of people who head to bed later than this group.
Previous research has suggested early risers fare better mentally because their extended exposure to sunlight generates a cascade of hormones that has a positive effect on mood. Other work has found that having a biological clock that works in opposition to most people — as night owls often do — can be isolating and depressing.
“We live in a society that is designed for morning people and evening people often feel as if they are in a constant state of misalignment with that societal clock,” Daghlas said, adding further study is needed to prove causation. “But this study definitely shifts the weight of evidence toward supporting a causal effect of sleep timing on depression.”
Approximately 11 per cent of men and 16 per cent of women in Canada will experience major depression at some point in their lives. Typically lasting two months or longer, major depression can result in feelings of hopelessness, detachment, lethargy, indecision and thoughts of suicide. The good news is depression can be treated and the first step is realizing that the troubling symptoms one experiences are not a personal failing but an illness for which help is available.
If you’re a night owl interested in seeing how the other half lives, Vetter recommends getting outside and getting moving soon after rising. “Keep your days bright and your nights dark,” she said. “Have your morning coffee on the porch. Walk or ride your bike to work if you can and dim those electronics in the evening.”
Dave Yasvinski is a writer with Healthing.ca
If you or someone you love is suffering from depression or another mood disorder, it’s important to remember you are not alone and there is nothing wrong with reaching out for help. There are a wealth of resources available online to help you better understand the symptoms of depression and how you can start on the road to recovery.