[Winter depression and light therapy].

Winter depression (Seasonal Affective Disorder, SAD) is a depressive illness, which starts in the autumn and disappears in the spring. The depression is, in contrast to the typical endogenous depression, characterized by increased appetite with carbohydrate craving, and increased sleep. There is an increase in the frequency of the illness towards the geographical poles. About 80% of the patients are women. The most remarkable aspect of the depression is however, that it can be effectively treated with bright light, given two hours daily for one to two weeks. A number of biological functions are currently under investigation in relation to winter depressions; among these are the metabolism of melatonin, various diurnal rhythms and the serotonergic system.