Sleep patterns are controlled by a regulation process called the circadian rhythm. Our arousal process, made up of specific brain cells, hormones, and chemicals keep us awake for about 16 hours before giving way to our sleep process, facilitated by different neurons, hormones, and chemicals. Our chronotype describes our sleep time preference, with 10% of us as early morning larks; 20% night owls; and 70% are hummingbirds, who fall asleep somewhere in between the larks and the owls.
A new study examined the relationship between chronotype and depression. Data from nearly 840,000 participants demonstrated that chronotype influenced risk of depression. Previous research had shown that night owls are up to twice as likely to suffer from depression as larks. In a study of 32,000 nurses, the larks were 27% less likely to develop depression over 4 years.
The new research confirmed that morning people suffer less from depression, but the study did not prove that being an early bird causes less depression. The data suggests that sleep timing patterns are a risk factor for depression. Researchers theorized that greater light exposure and more conformity to the norms of being awake during the day may explain these results. They suggested that owls and hummingbirds may want to set an earlier wake and bedtime, get as much daylight as possible, get outside early in the day, and prepare for the dark of sleep by limiting screen time close to bedtime.
Takeaway: If you tend to be a night owl, and you struggle with depression, consider gradually shifting your sleep schedule, along with maximizing your time outdoors during the day.
Debra S. Austin, Killing Them Softly: Neuroscience Reveals How Brain Cells Die from Law School Stress and How Neural Self-Hacking can Optimize Cognitive Performance, 59 Loy. L. Rev. 791, 837 (2013), online at https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2227155.
Daghlas I, Lane JM, Saxena R, Vetter C. Genetically Proxied Diurnal Preference, Sleep Timing, and Risk of Major Depressive Disorder. JAMA Psychiatry. Published online May 26, 2021. doi:10.1001/jamapsychiatry.2021.0959.