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Early birds have a lower risk of mental illness than night owls, show genes

Some people get out of bed at dawn, while for others, early morning is only an experience if they did not sleep last night.

Key points

  • A study of nearly 700,000 people found 324 new genes associated with body clocks.
  • Having more “early growth” genes meant that people were more likely to report a sense of well-being and were less likely to develop mental illness.
  • Understanding how biological clocks affect health can lead to more targeted treatment of mental illness.

But night owls take note: according to a large new study, people who are genetically programmed to get up early are less likely to have schizophrenia or depression.

“We show that morning man is causally linked to improved mental health,” an international team of researchers at Nature Communications said today.

A genetic study of nearly 700,000 people revealed more than 320 new genes in addition to the 24 genes that are known to affect whether someone is a morning person or a night owl.

People with the highest number of identified genes are likely to grow and shine 25 minutes earlier than the people with the least number.

Whether you are an early or late bird, depends on your biological clock, but very little is known about how your circadian rhythms affect the disease.

Previous studies have suggested that night owls are more prone to obesity or type 2 diabetes or depression, but it was unclear whether these conditions themselves affected when people slept or were caused by other factors, such as exercise, which are less common at night.

“This is the first large-scale study that examines a causal relationship between circadian rhythms and impaired health,” said co-author Enda Byrne of the University of Queensland.

“People have been studying circadian rhythms in the context of mental disorders for a number of years, looking for one gene at a time to understand it,” said Dr. Byrne.

"But this is a kind of big breakthrough in viewing the entire genome to find this link."

Circadian rhythm genes detected

The researchers analyzed the genetic variations of people who participated in the Biobank study in the UK and in the private American genetic company 23andMe.

Participants contributing to each database were asked to indicate whether they were morning or nocturnal to see which genes they share.

Along with genes associated with the regulation of circadian rhythms and insulin, genes associated with retinal cells were present in the eye, which capture light signals and send them to the brain.

“Light is the main influence of the environment that helps us synchronize our rhythms,” said Dr. Byrne.

Since self-reports may be inaccurate, the researchers also analyzed a subgroup of more than 85,000 people who were wearing activity monitors to get an objective assessment of the body clock behavior.

This showed that there was no connection between when people went to bed and the quality or duration of sleep.

“It was not the morning when people went to bed early, so they slept more than in the evening, which made them feel better,” said Dr. Byrne.

Surprisingly, genetically predisposed evening types were no longer at risk of obesity or type 2 diabetes than those who got up early.

There was, however, a small but statistically significant correlation between genetic variants, which increased the chances of becoming an owl and increased the risk of mental health conditions.

Dr. Byrne said that additional work is required to understand this connection.

“For example, it may happen that evening people are forced to get up early, which takes them out of their natural rhythm because of work, children or some other influence of the environment on their lives,” he said.

"This combination of genetic predisposition with environmental factors may be the cause of the symptoms of depression."

Effects for night owls

Ian Hickey from the Center for Brain and Mind at the University of Sydney said that genetic research confirmed what psychiatrists had been thinking about for a long time: mood disorders are associated with circadian rhythms, not sleep disorders.

He said that this explains why 20 years of research could not find sleep genes associated with mood disorders.

“They finally cracked the crap, saying,“ You know that we were looking at the wrong thing, ”said Professor Hickey, who did not participate in the study.

"This is not a dream, it is a body clock."

Professor Hickey said that the body clock had a period of wakefulness and sleep, and everyone had a normal setting, known as "morning sleepiness."

While people with a lot of morning genes had body watches that were well suited for 9–5 exercises, night owls did not.

Professor Hickey said that being an evening person does not mean that you are poorly motivated.

But being a night owl meant that your biological clock could be easily thrown away, and this can increase your susceptibility to mental illness.

Although it is not possible to become a “morning man,” Professor Hickey said that night owls can take steps to regulate their daily cycle in order to reduce the risk of developing mental illness.

"Night people should be very careful … they can very easily stay up all night."

Professor Hickey said that the results may lead to more effective mental health treatments based on the use of drugs such as light, exercise and melatonin-based drugs, instead of serotonin-based drugs used to treat sleep disorders.

“Now, of course, there is a lot of hope for the future if you have a genetic test before you choose the right medicine or behavioral treatment,” said Professor Hickey, adding that this is the subject of extensive research on depression and bipolar disorder, which currently time are spent in Australia.

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