Bimodal distribution of REM sleep latencies in depression

The REM sleep latency of endogenously depressed patients was investigated by analyzing 90 polysomnograms of six patients during depression and 58 polysomnograms of four of these patients after remission. During depression the REM sleep latencies are distributed bimodally with peaks at sleep onset (sleep onset REM phases, SOREMPs) and 60 min later. During the follow-up examinations some time after remission, the occurrence of SOREMPs is very rare. A model is proposed according to which the occurrence of SOREMPs in the sleep of these patients is caused by a reduced amplitude of the circadian rhythm of the arousal system.