Early return to REM sleep after nocturnal awakening in depression

Sixteen male outpatients with major depression and 20 age-equated healthy controls were awakened from rapid eye movement (REM) sleep between 1:30 and 3:30 AM, and the rapidity of return to REM sleep was determined. The time it took to return to REM sleep was reduced in depressives compared with controls: 61.6 (17.9 SD) min versus 80.6 (24.9 SD) min, respectively (p = 0.01). The time elapsed until the return to REM sleep was significantly correlated with baseline REM latency in controls (but not depressives). In contrast, return to REM time was significantly correlated with depression severity scores in depressives (but not controls). There was no evidence to support the hypothesis that the more rapid return to REM sleep in depression was caused by a slow wave sleep deficit. The mechanism underlying the rapid return of REM sleep in depression thus may be related to a severity-linked disturbance, such as a proposed increase in REM "pressure."