In our basic neuroscience series, we covered how essential sleep is to our general functioning. Amongst all of the many examples, poor sleep has been linked with depression, hereby, a recent study in the journal JAMA Psychiatry suggests that waking up one hour earlier could reduce a person’s risk of major depression by 23%.
The study, conducted by researchers at the University of Colorado Boulder and the Broad Institute of MIT and Harvard, represents some of the most compelling evidence yet that a person’s proclivity to sleep at a certain time influences one’s risk of depression. The findings also provided some of the first quantitative measures of how much, or how little, change is required to impact mental health.
The findings are particularly relevant as people go back to work and school following the pandemic, which for many drastically shifted their sleeping schedule.
Previous studies have found that night owls are up to twice as likely as early risers to suffer from depression, regardless of how long they sleep. However, because mood disorders can disrupt sleep patterns, researchers have had trouble determining the direction of causality in this relationship.
One of the researchers conducted a long-term study of 32,000 nurses in 2018 in which they found that “early risers” were up to 27% less likely to develop depression over the course of four years. This begs the question: what does it mean to be an early riser?
More than 340 common genetic variants are known to influence a person’s chronotype, including variants in the so-called “clock gene” PER2. In total, genetics accounts for 12-42% of our sleep timing preference.
The researchers analysed de-identified genetic data from up to 850,000 people, including 85,000 who wore sleep trackers for 7 days and 250,000 who filled out sleep-preference questionnaires. This provided them with a more detailed picture – down to the hour – of how gene variants influence when we sleep and wake up.
Roughly one-third of those polled identified as morning larks, 9% as night owls, and the rest as somewhere in the middle. The average sleep midpoint was 3 a.m., which means they went to bed at 11 p.m. and woke up at 6 a.m.
With this information, the researchers turned to a different sample that included genetic information, anonymized medical and prescription records, and surveys about major depressive disorder diagnoses.
The findings indicated that with each hour earlier the sleep midpoint (halfway between bedtime and wake time) was, this was associated with a 23% lower risk of major depressive disorder.
This means that if someone who normally goes to bed at 1 a.m. goes to bed at midnight instead and sleeps the same amount of time, they can reduce their risk by 23%; if they go to bed at 11 p.m., they can reduce it by 40%.
According to the study, those who are already early risers may benefit from getting up even earlier. However, for those in the intermediate or evening range, shifting to an earlier bedtime would most likely be beneficial.
The findings could be corroborated by research suggesting that getting more light exposure during the day, which early risers tend to get, causes a cascade of hormonal effects that can influence mood.
Daghlas, I. et al., 2021. Genetically Proxied Diurnal Preference, Sleep Timing, and Risk of Major Depressive Disorder. JAMA Psychiatry.
Photo by Andrea Piacquadio from Pexels
Edited by Cyrus Rohani-Shukla