Circadian Rhythm Disorders: Phase-Advanced and Phase-Delayed Syndromes: Phase-Advanced & Phase-Delayed Syndromes

The circadian rhythm sleep disorders of delayed sleep phase disorder (DSPD) and advanced sleep phase disorder (ASPD) are associated with circadian rhythms timed too late and too early, respectively. Because of the potent effect of the circadian rhythms on sleepiness/alertness, these timing abnormalities can then lead to sleep onset difficulties or early morning awakening insomnia, respectively. The timing differences may arise from circadian period lengths longer or shorter than 24 hours, differential responsiveness to the phase delaying or advancing effects of bright light, differences in accumulation rate of homeostatic sleep drive, or subjective sleepiness rhythm differences. In any case, chronobiologic interventions including bright light therapy and melatonin administration are indicated as treatment in addition to appropriate behavioral and cognitive therapies. Furthermore, the overlap between DSPD with sleep onset insomnia and ASPD with useful adjunct to the present cognitive/behavioral treatment package for insomnia.