[Seasonal affective syndrome and phototherapy: theoretical concepts and clinical applications].

Since 1984, there has been a great interest in the phenomenon of a particular seasonally recurrent mood disorder called seasonal affective disorder (SAD) or winter depression and its treatment: the phototherapy. Seasonal affective disorder is a syndrome described by Rosenthal in 1984. This mood disorder is characterized by depression with onset recurrent in autumn or winter and spontaneous spring or summer remission. It is associated with hypersomnia, anergia, increased appetite, weight gain and carbohydrate craving. The population prevalence in the north of the USA is estimated between 3 and 5%, but it changes with sex, age and also latitude. A long time ago, we know that animals are photoperiod sensitive and that the melatonin secretion in mammals is suppressed by the light. In 1980, Czeiler reported for the first time that human melatonin secretion can be suppressed by high light exposure (+/- 1500 lux). In 1982, Rosenthal, Lewy and al. reported an antidepressant effect of light exposure of a manic-depressive patient. The phototherapy was born. To treat the SAD, the most common procedure of phototherapy is to expose the subject during 2 hours early in the morning, between 06:00 and 09:00 AM. The subject is sitting before a light screen, he can work and has to fix the screen one time every minute. The most common side effects are headache, eyestrain, muscle pain. The ocular phototoxicity is controversed and it seems to be potentially dangerous if phototherapy is associated with tricyclic antidepressants, neuroleptics and other medication containing a tricyclic, heterocyclic or porphyrin ring system. Since this finding, many questions are asked about photoperiod and its effects in the human being. Lewy proposes for the winter depression the hypothesis of a phase delayed circadian rhythm, that can be treated by a morning light exposure. At the present time, many trials are going on to study the effects of phototherapy in other problems like insomnia, maladaptation to night work, jet lag and Alzheimer disease.