The study, published in the Lancet Physchiatry, used data from 91,105 participants to obtain a measure of daily rest and activity rhythms, which is called relative amplitude. Individuals with lower relative amplitude were at greater risk of several adverse mental health outcomes, even after adjusting for confounding factors, such as age, sex, lifestyle, education and previous childhood trauma.
Circadian rhythms are variations in physiology and behaviour that recur every 24 hours, such as the sleep-wake cycle and daily patterns of hormone release. Circadian rhythms occur in plants, animals and throughout biology. They are fundamental for maintaining health in humans, and integrity of circadian rhythms is particularly important for mental health and wellbeing.
Dr Laura Lyall, lead author, said: “In the largest such study ever conducted, we found a robust association between disruption of circadian rhythms and mood disorders. Previous studies have identified associations between disrupted circadian rhythms and poor mental health, but these were on relatively small samples.”
Professor Daniel Smith, Professor of Psychiatry and senior author, said: “This is an important study demonstrating a robust association between disrupted circadian rhythmicity and mood disorders.
“The next step will be to identify the mechanisms by which genetic and environmental causes of circadian disruption interact to increase an individual’s risk of depression and bipolar disorder.
“This is important globally because more and more people are living in urban environments that are known to increase risk of circadian disruption and, by extension, adverse mental health outcomes.”