The number of locations in the human genome known to play a role in the circadian rhythm now stands at 351, thanks to the research, up from 24. The team found that the genetic areas influence sleep timing but not quality or duration.
The genomic regions identified include those central to our body clocks, as well as genes expressed in the brain and in retinal tissue in the eye. The body-clock cycle is slightly longer than the 24-hour daily cycle and the eye tissue connection may help explain how the brain detects light to reset the body clock each day.
Dr Mike Weedon, who led the research at Exeter, said: "The large number of people in our study means we have provided the strongest evidence to date that night owls are at higher risk of mental health problems, such as schizophrenia and lower mental wellbeing, although further studies are needed to fully understand this link."
The body clock is influenced by genes and lifestyle factors including diet, exposure to artificial light and jobs and activities. The study is published in Nature Communications.
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