A major new study published in medical journal The Lancet Psychiatry reveals a link between a disrupted body clocks and bi-polar disorder.
It found people who were more active a night were at greater risk of developing mood disorders and depression.
Scientists recorded data from more than 91,105 people wearing a sleep detecting device on their wrist for seven days to see how sleep — or lack of sleep — affect their mood.
The researchers from University of Glasgow examined sleeping patterns, body temperature, immune systems, hormones to measure body rhythms.
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They concluded that body clock disruptions were reliably associated with depression and bipolar disorder.
Professor Daniel Smith, senior author of the paper, told The Times: "It's not just what you do at night, it's what you do during the day — trying to be active during the day and inactive in darkness."
"This is an important study demonstrating a robust association between disrupted circadian rhythmicity and mood disorders," says Professor Smith.