Scientists think they've found a way to massively cut the risk of depression - that's the good news. The bad? It involves getting up an hour or two earlier each day.
Forcing yourself into bed and out of it again 60 minutes earlier than what feels right can reduce the likelihood of a major depressive disorder by 23 percent, a massive new study has found.
If you have the willpower to hit the sack 120 minutes earlier, the risk is cut by 40 percent.
"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 Celine Vetter, assistant professor of integrative physiology at CU Boulder, and senior author of the study.
"We found that even one-hour earlier sleep timing is associated with significantly lower risk of depression."
Until now it's been unclear whether people who stayed up later were more likely to develop depressive symptoms, or whether people with depressive symptoms stayed up late.
To solve the mystery, scientists looked at genetic data belonging to hundreds of thousands of people, many which had either worn sleep trackers or filled out a questionnaire, and others with a history of depression.
The found "firm" evidence it's the time that people go to bed that influences their state of mind, not so much the other way around.
But why? Previous research suggests it's that early risers get more light exposure, which can positively affect mood; and night-owls - about 9 percent of those in the study - have trouble staying in sync with the rest of us.
"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 of Harvard Medical School. "This study definitely shifts the weight of evidence toward supporting a causal effect of sleep timing on depression."
"Keep your days bright and your nights dark," said Dr Vetter. "Have your morning coffee on the porch. Walk or ride your bike to work if you can, and dim those electronics in the evening."
The study was published in journal JAMA Psychiatry.
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