Waking one hour earlier cuts depression risk by 23%, study suggests

Whether it's starting the day with an exercise class or ticking something off your to-do list, many have good intentions when setting an early alarm.

The allure of the snooze button is often all too tempting, however, new research suggests early risers may be less at risk of depression.

Scientists from the University of Colorado at Boulder analysed the genetics and sleep habits of more than 840,000 people.

Results suggest waking one hour earlier cuts a person's risk of major depressive disorder, "a serious and debilitating" form of the mental health condition, by 23%.

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Rising two hours earlier was linked to 40% lower odds of depression.

Although it is unclear why this occurs, morning larks may have greater exposure to natural light, which then has a cascade effect on their hormones, boosting their mood.

"We have known for some time 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 study author Dr Celine Vetter.

"We found even one hour earlier sleep timing is associated with [a] significantly lower risk of depression."

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To help ward off the condition, Vetter recommends people "keep their days bright and their nights dark".

"Have your morning coffee on the porch," she said.

"Walk or ride your bike to work if you can, and dim those electronics in the evening."

Sleep has long been linked to depression, with a lack of shut eye known to both trigger and exacerbate the mental health condition.

Night owls are generally more at risk than morning larks, even if they both sleep for the same number of hours overall.

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With previous studies being small or of low quality, the Colorado scientists analysed data from the DNA testing company 23 and Me, as well as participants of the UK Biobank study.

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The results suggest more than 340 genetic variants – including those to the so-called "clock gene" PER2 – affect a person's chronotype, defined as their propensity to sleep at a certain time.

The scientists concluded a person's genetics influence between 12% and 42% of their sleep-timing preferences.

They then honed in on the data of 850,000 people, of whom 85,000 wore a sleep tracker for one week and 250,000 completed a sleep-preference questionnaire.

Overall, around a third of the participants self-identified as being morning larks, while just under one in 10 (9%) were night owls, with the remainder slotting in the middle.

To better understand how sleep timing influences depression, the scientists compared the participants' genetic information to any prescriptions or depression diagnoses.

The results, published in the journal JAMA Psychiatry, suggest both going to bed and rising earlier cuts the risk of depression.

This may only apply to night owls or those in the middle sleep-preference range, rather than people who are already morning larks, according to the scientists.

Although it is unclear, having a biological clock that is skewed towards late nights could lead to depression in itself.

"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 Dr Iyas Daghlas.

The scientists have stressed a larger study is required to confirm their results.

Nevertheless, "this study definitely shifts the weight of evidence toward supporting a causal effect of sleep timing on depression", said Dr Daghlas.

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