[Phototherapy in the clinic]

From early centuries sun light has been considered as a source of life energy and a life donor. Seasonal changes in human behaviour and mood have been already described in details by psychiatrists since the beginning of the XX century. In the last twenties systematic studies on animals and humans have provided the evidence that bright light is the strongest exogenous synchronizer of endogenous biological rhythms. In some people bright light deficiency induces changes of mood and symptoms of the seasonal affective disorder (SAD). SAD is characterised by fall and winter depressions, hypersomnias, augmented appetite with carbohydrate cravings, and weight gain alternating with non-depressed periods with normal behaviour in the spring and summer. There is also a minor depressive form of the illness called sub-syndromal (S-SAD) or "winter blues". The molecular mechanisms of this disorder remine unknown. In the last decade the few hypothesis on the etiology of SAD, confirming experimentally more or less, have been developed. From the beginning of eighties SAD is successfully treated with bright light (phototherapy). This way of the natural treatment can be also used in Circadian Rhythm Sleep Disorders such as Jet Lag Syndrome, Shift Work Sleep Disorder or others. An application of phototherapy in clinic gives opportunity for the progress of a new way of treatment--chronotherapy and it seems to be the attainment of chronobiology in practical medicine.