Circadian rhythm disruptions have been linked to mood disorders such as depression and bipolar disorder. These rhythms are nothing but natural variations that occur in a day in our behaviors. The findings of this study are published in the Journal of Applied Physiology.
The new study has found that disrupted circadian rhythms have been associated with increased risk of mood disorders, including depression and bipolar disorder. Circadian disruption was also associated with lower subjective well being, higher neuroticism and greater mood instability.
Circadian rhythms are variations in physiology and behavior 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 well being.
Dr. Laura Lyall, the 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."
In addition to increased risk of depression and bipolar disorder, lower relative amplitude was also associated with low subjective ratings of happiness and health satisfaction, with a higher risk of reporting loneliness, and with slower reaction time (an indirect measure of cognitive ability).
A lower circadian amplitude denotes less distinction, in terms of activity levels, between active and rest periods of the day. This can be due to reduced activity during waking periods or increased activity during rest periods. Shifts in energy levels and sleep disturbances are common during the clinical depression and episodes of bipolar disorder.
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 the risk of circadian disruption and, by extension, adverse mental health outcomes."
The study, 'Association of disrupted circadian rhythmicity with mood disorders, subjective well-being and cognitive function: a cross-sectional study of 91,105 participants in the UK Biobank cohort' is published in The Lancet Psychiatry. The work was funded by a Lister Prize Fellowship to Professor Smith.