[Sleep-wakefulness rhythm disorders].

The circadian system is synchronized on 24-hour by the light-dark synchronizer and by the social time cue. The circadian rhythm sleep disorders share a common underlying chronobiological basis. These disorders may be due to either jet-lag, shift-work or to lesions of the peripheral visual pathway. The delayed sleep phase syndrome, the advanced sleep phase syndrome, the non 24-hour syndrome as well as the irregular sleep-wake patterns are described. Therapeutic approaches, in particular with melatonin and (or) bright light, are presented.