What’s New in Psychology?

A Way to Cut the Risk of Depression

Jim Windell

            The best way to stay healthy and avoid depression is to get plenty of sleep, right? Sleep longer and later in the morning and you will wake up refreshed and better able to fight off any tendencies toward depression. In fact, since the pandemic, you may have been able to sleep later – instead of getting up early to go to work.

            All of which sounds like a good prescription, but what does research say?

            A new study, recently published in JAMA Psychiatry, suggests this is the wrong way to cut the risk of depression.

           Researchers at the University of Colorado Boulder and the Broad Institute of MIT and Harvard studied 840,000 people. In the study, the researchers looked at the data from 85,000 individuals who had worn wearable sleep trackers for seven days and 250,000 who had filled out sleep-preference questionnaires. This gave them a more granular picture, down to the hour, of how variants in genes influence when we sleep and wake up.

           In the largest of these samples, about a third of surveyed subjects self-identified as morning larks, nine percent were night owls and the rest were in the middle. Overall, the average sleep mid-point was 3 a.m., meaning they went to bed at 11 p.m. and got up at 6 a.m.

           With this information in hand, the researchers turned to a different sample which included genetic information along with anonymized medical and prescription records and surveys about diagnoses of major depressive disorder. Using novel statistical techniques, they asked a simple question: Do those with genetic variants which predispose them to be early risers also have lower risk of depression?

           The answer? They found that answer was a decided yes.

           Each one-hour earlier sleep midpoint (halfway between bedtime and wake time) corresponded with a 23% lower risk of major depressive disorder.

           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. However, what causes what has perplexed researchers. Mood disorders themselves can disrupt sleep patterns and that may cause some people to be night owls. In addition, 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 – which could confound results.

           "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 senior author Celine Vetter, assistant professor of integrative physiology at CU Boulder. In 2018, Vetter published a large, long term study of 32,000 nurses showing that "early risers" were up to 27% less likely to develop depression over the course of four years. But that led to a further question: What does it mean to be an early riser?

           This study is among the first studies to quantify just how much, or little, change is required to influence mental health. "We found that even one-hour earlier sleep timing is associated with significantly lower risk of depression," Vetter said.

           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%.

           It's unclear from the study whether those who are already early risers could benefit from getting up even earlier. But for those in the intermediate range or evening range, shifting to an earlier bedtime would likely be helpful.

           What could explain this effect?

           Some research suggests that getting greater light exposure during the day, which early-risers tend to get, results in a cascade of hormonal impacts that can influence mood. Others note that having a biological clock, or circadian rhythm, that trends differently than most peoples' can in itself be 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," said lead author Iyas Daghlas, M.D.

           For those wanting to shift themselves to an earlier sleep schedule, Vetter offers this advice: "Keep your days bright and your nights dark," she says. "Have your morning coffee on the porch. Walk or ride your bike to work if you can and dim those electronics in the evening."

           To read the original journal article, find it with this reference:

Daghlas, I., Lane, J.M., Saxena, R., & Vetter, C. (2021). Genetically Proxied Diurnal Preference, Sleep Timing, and Risk of Major Depressive Disorder. JAMA Psychiatry; DOI: 10.1001/jamapsychiatry.2021.0959