The phenomenon of "winter depression" for a long time not recognized scientists. However, the facts speak for themselves. Many people really feel overwhelmed, when it is cold outside, and daylight hours are short. The worst weather situation in the Nordic countries.
The shortage of sunlight leads to enhanced production of melanin, the excess substances causes fatigue and constant sleepiness. Further analysis of the problem has allowed to draw deeper conclusions about the nature of seasonal depression.
The transition to winter time and a quick shift of day length in the direction of long nights and short days provoke discomfort and fatigue.
Scientists advise more time to be outdoors, play sports. The Solarium is a great option replenish vitamin D. Note that while the question of "winter depression" were not studied thoroughly. More research is needed to establish the mechanisms of disease development.