REM-SLEEP DISINHIBITION AT SLEEP ONSET - A COMPARISON BETWEEN NARCOLEPSY AND DEPRESSION

Shortened REM latency and increased REM density are frequently observe d in both narcolepsy and depression, suggesting a common mechanism of REM sleep disinhibition in these disorders. We compared night sleep re cordings of 24 depressive and 24 narcoleptic patients. The amount of R EM sleep and REM density did not differ between the patient groups; ho wever; REM latency distributions differed significantly. Whereas in na rcoleptic patients REM episodes started either immediately at sleep on set or following at least 60 min of non-REM sleep, in depressives two thirds of REM latencies were in the range from 1 to 60 min. In narcole ptic patients, short as compared to long REM latencies were associated with longer total sleep time, greater sleep efficiency, reduced amoun ts of wakefulness, and increased amounts of slow-wave sleep. In depres sive subjects the reverse pattern was seen., We conclude that a common mechanism of REM sleep disinhibition in narcolepsy and depression is very unlikely. (C) 1992 Society of Biological Psychiatry.