A new collaborative large-scale genomic analysis from researchers at the University of Exeter and Massachusetts General Hospital reveals new information about the human body clock and how it may be linked to mental health and disease.
The study, published January 29th in Nature Communications, found that those genetically programmed to be early risers had a greater well-being and less risk for developing schizophrenia and depression.
250,000 U.S. participants from private genomic analyst company 23andMe, and 450,000 U.K. participants from the U.K. Biobank were gathered for the study. Each participant was asked whether they were a “morning person” or a “evening person.” Based on their answer, researchers then looked at their genes to see if morning people and evening people shared common genes amongst their group that influence their sleep patterns.
Then, using wrist-worn activity trackers worn by 85,000 of the U.K. participants, researchers found that the genetic variants they identified could shift a person’s natural waking time by about 25 minutes. However, these genetic variants did not affect quality or duration of sleep.
“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 Professor Mike Weedon, from the University of Exeter Medical School. “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 well-being, although further studies are needed to fully understand this link.”
The genetic areas that affect waking times are those essential to our body clock — our circadian rhythms. They are also genes expressed in the brain and the eye’s retinal tissue, which could explain how the brain detects light and orders the body to “reset,” or go to sleep.
Our body clocks are affected by numerous factors such as genetics, exercise, diet, daily activities, and our exposure to artificial light, and can determine hormone levels, body temperature, and our waking and sleep patterns.
“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,” lead author Dr. Samuel E. Jones, of the University of Exeter Medical School, said. “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.”
Dr. Jacqueline M. Lane, of the Massachusetts General Hospital Department of Anesthesia, added that knowing how our genetic body clock works can help professionals treat their patients with delayed circadian rhythm disorders.
“We know that there are links between how the body clock functions and our health and wellbeing but, to date, we have understood little about the part genetics plays,” said Dr. Rachael Panizzo, Programme Manager for Mental Health and Addiction at the Medical Research Council. “Now, with the help of publicly funded datasets like UK Biobank, researchers are able to study on an unprecedented scale, the interplay between the genetics of the body clock and the risk of mental health conditions such as schizophrenia and depression. This study provides valuable new insights which we hope will lead to more effective interventions for those most at risk.”