Waking up just one hour earlier cuts depression risk

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Waking up just one hour earlier could reduce a person's risk of major depression by 23 per cent, suggests a sweeping new genetic study.<br />
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The study indicates that if someone who normally goes to bed at 1 a.m. goes to bed at midnight instead and sleeps the same duration, they could cut their risk by 23 per cent; if they go to bed at 11 p.m., they could cut it by about 40 per cent.<br />
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"We found that even one-hour earlier sleep timing is associated with significantly lower risk of depression," said researcher Celine Vetter from the University Of Colorado At Boulder.<br />
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Some research suggests that getting greater light exposure during the day, which early-risers tend to get, results in a cascade of hormonal impacts that can influence mood.<br />
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Others note that having a biological clock, or circadian rhythm, that trends differently than most peoples' can in itself be depressing.<br />
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For the study, published in the journal JAMA Psychiatry, the team turned to data from a DNA testing company and the biomedical database UK Biobank. They then used a method called "Mendelian randomisation" that leverages genetic associations to help decipher cause and effect.<br />
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More than 340 common genetic variants, including variants in the so-called "clock gene" PER2, are known to influence a person's chronotype, and genetics collectively explains 12-42 per cent of our sleep timing preference.<br />
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The researchers assessed de-identified genetic data on these variants from up to 850,000 individuals, including data from 85,000 who had worn wearable sleep trackers for 7 days and 250,000 who had filled out sleep-preference questionnaires.<br />
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In the largest of these samples, about a third of surveyed subjects self-identified as morning larks, 9 per cent were night owls and the rest were in the middle. Overall, the average sleep mid-point was 3 a.m., meaning they went to bed at 11 p.m. and got up at 6 a.m.<br />
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With this information in hand, the researchers turned to a different sample which included genetic information along with anonymised medical and prescription records and surveys about diagnoses of major depressive disorder.<br />
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Using novel statistical techniques, they asked: Do those with genetic variants which predispose them to be early risers also have a lower risk of depressionIJ The answer is a firm yes, the study noted.<br />
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