It is known that hormones affect various processes of the body’s functioning and its general condition. The idea of ​​the biochemical causes of various kinds of mental disorders is supported by many medical researchers. So, the hormone melatonin (or the sleep hormone), which is responsible for the sleep and wakefulness cycle, at its low rate can cause insomnia, which entails a decrease in stress resistance , rapid fatigue, low concentration of attention, which, subsequently, may cause depression. Melatonin is a derivative of the hormone serotonin, whose quantitative changes can affect mood and appetite (its lack contributes to the appearance of neuroses, eating disorders).              

During seasonal changes, due to changes in the length of daylight hours, the amount of hormones may vary. Melatonin is actively released in the dark, dissipates in sunlight. In summer hormones in its amount regulated with the expense of short periods of night, at the same time in the autumn and winter period, the number of melatonin is increased, which can contribute to poor health, dizziness and reduce body temperature, giving rise to the fall of depression.            

In animals, melatonin affects the regulation of the hibernation period, the degree of activity, thus, for winter, the animal’s body gradually prepares itself for a state of long rest. In accordance with this, the human body also slows down its processes, which affects the degree of activity and the need for rest. In general, the human body has fully adapted to such changes in hormonal balance, but there are people who are sensitive to such changes.             

Seasonal depression, or seasonal affective disorder, becomes for them a form of manifestation of seasonal changes in the amount of melatonin, expressed in the following symptoms: 

•  drowsiness;
•  apathy;
•  decreased concentration of attention;
• violation of appetite;
•  Bad mood.

In connection with this, seasonal depression is treated by the use of light therapy , which involves subjecting artificial light on human. Also, frequent walks on a sunny day are recommended , if possible, spending a winter vacation in southern countries. In drug treatment, various groups of antidepressants are used, which help to regulate the production of melatonin, as well as increase serotonin. It is necessary to understand that the synthesis of one hormone can lead to a deficiency of another, or if the melatonin level is low, the production of serotonin may also be low , this in practice demonstrates the connection between depressive disorder and sleep disorders. The regulation of hormone levels can also occur naturally, if certain foods are consumed in sufficient quantities. For the regulation of melatonin, foods containing complex carbohydrates are needed: bananas, milk, rolled oats. To increase serotonin levels, it is recommended to consume: nuts, seafood, seeds.