Disorders of circadian rhythms correlate with depression, bipolar disorder and neuroticism.

Sleep is very important for the brain. Like other animals and plants, the human body functions in accordance with circadian rhythms - cyclical fluctuations in the intensity of biological processes associated with the alternation of day and night. Circadian rhythms have an endogenous origin, that is, they are caused by internal factors, and not by external influence. Even if the animal is permanently placed in total darkness, the circadian rhythms will not disappear anywhere, and the cyclical fluctuations of biological processes will continue to be observed in accordance with the biological clock approximately every 24 hours.



For human babies, there are special robots that rock the baby and quickly put the baby to sleep if it makes sounds and moves. But in adults, the procedure for bedtime is much more complicated - usually it includes a chain of rituals and hygienic procedures. And recently, in this chain, many adults include viewing messages on a smartphone. And absolutely nothing. Doctors warn that this is a very risky behavior /



Previous studies have convincingly proved the harm to the body of a violation of 24-hour circadian rhythms, for whatever reason they occur, be it a night shift at work or entertainment in a nightclub. In any case, the body has serious negative consequences.



Now scientists from the University of Glasgow have conducted the most large-scale experiment in the history of studying the failure of biological clocks in humans. For research in the UK Biobank database, a sample of 91,105 people between the ages of 37 and 73 years old were taken, who for seven days in 2006–2010 wore on their wrist accelerometers that track physical activity.



Of course, the research methodology is not without flaws, because only the behavior of middle-aged and elderly people was studied, and the seven-day experiment does not allow to draw conclusions about the long-term effects of sleep disorders. But the researchers carefully adjusted the model, eliminating the influence of any extraneous factors.



Approximately 4% of the subjects found unusual patterns of activity, when their activity during the day practically did not differ from activity at night. It could be night shifts at work, parties at clubs, computer work, and so on. In any case, these people did not obey the natural natural clock, that is, the circadian rhythms of the body.



It is not surprising that such disobedience to the laws of nature correlates with mental health disorders. Scientists have determined that in this sample of people the probability of bipolar disorder is 11% higher than the average, and the probability of depression is 6% higher.



In addition, these people also reported lower levels of happiness and more experienced loneliness.



Of course, as in all such studies, it is impossible to determine the cause and effect. Either mental illnesses force people to knock down their biological clocks and resist circadian rhythms, or vice versa - failure of circadian rhythms leads to mental disorders. But the fact is that these two phenomena correlate with each other, and healthy sleep is extremely important for maintaining mental health.



Lead author of the work, psychiatry professor Daniel Smith from the University of Glasgow talks about the so-called “poor sleep hygiene” when people engage in some kind of activity late at night, including playing on mobile phones or drinking tea. “This important study demonstrates a clear link between disturbed circadian rhythms and mood disorders,” said the professor. - The next step will be to identify the mechanisms by which the genetic and environmental causes of circadian rhythm disturbances interact, increasing the risk of depression and bipolar disorder in humans. This is important all over the world, because more and more people live in urban environments that are known to increase the risk of circadian circulatory dysfunction and, consequently, adverse mental health consequences. ”



At night in modern cities there is too much noise and artificial lighting, and during the day people spend time in rooms that are closed from sunlight (illumination is less than 4000 lux). All this makes the circadian rhythms beat down a bit.



The scientific article was published on May 15, 2018 in the journal Lancet Psychiatry (doi: 10.1016 / S2215-0366 (18) 30139-1).