In a major finding published in the journal JAMA Psychiatry, scientists report that one’s sleep schedule can influence risk of depression. Your sleep schedule is largely determined by your chronotype—your circadian rhythm, which is your internal clock. This can determine your propensity to be high energy or sleepy at certain times of the day. Researchers found that people predisposed by genetics to be early risers firmly have a lower risk of depression.

The study

Genetics can explain up to 42 percent of our sleep timing patterns. Researchers from the University of Colorado Boulder and the Broad Institute of MIT and Harvard explored depression risk based on chronotype. They obtained sleep data using DNA testing brand 23andMe as well as biomedical database UK Biobank.

With data from up to 850,000 individuals, the researchers categorized subjects into three groups: Morning larks, night owls and those in-between. They then analyzed this information in relation to genetic data, plus medical and prescription records and diagnoses of major depressive disorder.

The findings

An analysis of the data reported that people with a chronotype supporting earlier sleep and wake times corresponded with lower risk of depression.

For every one-hour earlier sleep midpoint—meaning, the time halfway between bedtime and wake time—subjects had a 23 percent lower risk of major depressive disorder. The earlier people went to bed, the better they tended to feel.

Say for example, you normally go to bed at 1am, sleep nine hours and wake at 10 a.m.. You then move your schedule up one hour, now going to bed at midnight, still sleeping for nine hours and waking at 9 a.m. You may be able to cut your risk of depression by 23 percent. If you went to bed yet another hour earlier, you could cut risk of depression again by roughly another 23 percent.

While the study finds that people with earlier sleep-and-wake schedules had lower risk of depression, it doesn’t conclusively determine exactly why. But the researchers have several theories:

• Light exposure: Early risers who wake before or with the sunrise tend to experience more sunlight in their day. Exposure to sunlight is associated with increased release of a hormone called serotonin. This hormone is responsible for boosting mood and increasing calmness and focus.
• The social clock: While many people are not genetically predisposed to sleeping and waking early, society indiscriminately promotes a bias towards morning-time. “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 the study lead author Iyas Daghlas, M.D. Living in a cycle that differs from what most people in society are compelled to follow can be isolating and, therefore, depressing.

What can I do to fight depression?

This novel study is among the first to clearly quantify how much change is required to affect your mental health. It found that shifting your sleep-and-wake clock by just one hour can decrease depression significantly. It also found that shifting by multiple hours had a cumulative effect on the quantity of improvement.

Ask yourself if you are experiencing a social dissonance in terms of the internal clock you feel compelled to live by. Do you find that you sleep and wake at a different time from most people around you? Does your inner clock not correspond with the hours demanded by your responsibilities, like your workplace or school? This may be because you have a night owl’s chronotype.

But can you permanently change your sleep cycle if you are genetically predisposed to a certain schedule? Our chronotypes are largely determined by our genetics, and therefore it can be hard to make a major change that goes against what is natural for our bodies. However, this shift need not be dramatic. As demonstrated by the study, just a one-hour change may notably decrease risk of depression. You only have to shift your sleep schedule 1-2 hours earlier than your norm to experience improvement.

Habits to gain control over your sleep cycle:

• Keep your days bright: Exposure to sunlight increases production of the happy hormone serotonin. Make it easier for yourself to stay awake by spending more daytime hours in sunlight. Take your morning coffee outside, go for a midday walk and take as many daytime breaks in sunlight as possible.
• And keep your nights dark: In contrast to the above, exposure to darkness increases production of the sleepy hormone melatonin. Make it easier to go to sleep by darkening your room as much as possible. Turn off all lights, close curtains and turn off electronic devices that emit blue light, e.g., laptops, computers, phones, etc.
• Have a nighttime routine and morning routine: Practice a consistent routine for both morning and evening. Your pre-bedtime routine should be calming, such as turning off screens, taking a hot bath, or pouring a sleep-supportive nightcap. Your morning routine should encourage wakefulness, like a cool glass of mint-infused water, a brisk shower, or a light jog.
• Do what you know: Nobody knows you as well as you know yourself. This means you know better than anyone what activities keep you awake versus make you sleepy. Struggling to sleep earlier than usual? Put away the distractions that keep you up, like playing on your phone. Instead, opt for an activity you know makes you sleepy, such as reading a thick book or playing soothing music.
• Don’t change how long you sleep: You’re looking to change when you sleep and wake up, not how many hours of sleep you get. Changing your cycle can mean a rough initial night or two at night. However, this disruption should not be permanent. Aim to get exactly the same number of hours of rest — just within a slightly different window.