In a new study, researchers from the University of Glasgow find that genetically, the body clock, or circadian rhythms, are linked to mood disorders like depression and bipolar disorder.
This is the largest ever genetic study of circadian rest-activity cycles in humans.
Block clock regulars 24-hour variations in behavior and activity that control many aspects of our lives, from hormone levels to sleeping and eating habits.
The body clock occurs in plants, animals and throughout biology. It is fundamental for maintaining health in humans, particularly mental health and wellbeing.
Previous research has found that disrupted body clock is linked to increased risk of mood disorders, including major depression and bipolar disorder.
In the new study, the researchers used genetic information and activity data from 71,500 participants in the UK Biobank cohort to obtain an objective measure of daily rest-activity rhythms, called relative amplitude.
They identified two areas of the human genome that may contain genetic variants that increase risk of disruption to rest-activity cycles.
One of these areas contained the gene Neurofascin, which binds to the protein product of a well-known candidate gene for bipolar disorder (Ankyrin G).
This suggests a direct biological link between body clock disruption and severe mood disorder. Genetic loading for circadian disruption was also significantly associated with mood instability.
The team suggests that disrupted rest-activity cycles have a biological basis, and are not simply the result of random or environmental circumstances.
The finding also implies that the link between disrupted rest-activity cycles and mood disorders may originate in the action of such genes.
Daniel Smith, Professor of Psychiatry, is the senior author.
The study is published in EBioMedicine.
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