Research says ‘night owls’ may be at greater risk due to having to fight natural body clock

This article is more than 1 year old

This article is more than 1 year old

People who are naturally early risers are less likely to develop mental health problems than “night owls”, according to scientists.

A large-scale genetics study found being biologically programmed to wake up early is linked to greater happiness and a lower risk of schizophrenia and depression.

The scientists behind the work said evening types may be at greater risk from the mental toll of having to fight their natural body clock due to most schools and workplaces having early start times.

Prof Mike Weedon, who led the research at the University of 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 study used genetics data from 250,000 research participants signed up to the private genetics company 23andMe, and 450,000 people in the UK Biobank study. Participants were asked whether they were a “morning person” or an “evening person”, and their genomes were analysed, revealing certain genes people shared that appeared to influence sleep patterns.

The latest findings increase the number of areas of the genome known to influence whether someone is an early riser from 24 to 351.

“This study highlights a large number of genes which can be studied in more detail to work out how different people can have different body clocks,” said Weedon.

The researchers also compared the genetics analysis to data from wrist-worn activity trackers collected from more than 85,000 individuals in the UK Biobank. This showed the genetic variants the researchers identified could shift a person’s natural waking time by up to 25 minutes, for example changing your average waking time from 7am to 7.25am.

The genes identified appeared to influence the time people went to sleep and got up, but not the quality or duration of sleep.

The evidence for a link between body clock and schizophrenia was the most compelling, with evening types being roughly 10% more likely to develop the condition. The data suggested morning people were also at lower risk of depression and reported being happier on wellbeing questionnaires.

Samuel Jones, the paper’s lead author, said: “Our work indicates that part of the reason why some people are up with the lark while others are night owls is because of differences in both the way our brains react to external light signals and the normal functioning of our internal clocks.

“These small differences may have potentially significant effects on the ability of our body clocks to keep time effectively, potentially altering risk of both disease and mental health disorders.”

Jones said the working hypothesis is that evening types are more likely to have to work against their natural body clock in school and the world of work, which may have negative consequences. Another possibility is the genes involved in determining the body clock have a more direct genetic influence on vulnerability to certain conditions.

The team is now aiming to address this question by looking at whether those whose lifestyles and body clocks are most mismatched are at greatest risk.

Some of the genes identified are known to be expressed in the brain and retinal tissue in the eye, which plays an important part in coupling our internal circadian rhythm to external cues.

Without any outside influence, the human body clock runs on a cycle that is slightly longer than 24 hours, and light sensitive cells in the retina help “reset” the body clock each morning to keep us aligned with the day-night cycle.

Despite previous findings linking sleeping habits to risk of diabetes and obesity, the latest work did not find any links between these conditions and body clock genes.

The body clock is influenced by genes and lifestyle factors including diet, exposure to artificial light and jobs and activities. It affects a wide range of molecular processes, including hormone levels and core body temperature, as well as waking and sleeping patterns.

The findings are published in the journal Nature Communications.