Rapid eye movement latency and mood following a delay of bedtime in healthy subjects: do the effects mimic changes in depressive illness?

Abstract

The phase advance hypothesis proposes that a phase advance of certain circadian rhythms (such as rapid eye movement (REM) sleep propensity) relative to the sleep-wake cycle is implicated in the pathophysiology and pathogenesis of depression. In an earlier study, we reported that a 6-h delay of sleep in normals produced REM changes that resembled the depressive pattern. Mood change was generally modest, although 2 of the 10 subjects became noticeably depressed. This study assessed the replicability of these results, and introduced a phase advance control condition. Predicted changes were observed in REM parameters. Modest but reliable mood change was confined to the first night of the phase delay, and was attributed to sleep loss. These results suggest that the effects of the phase shift were relatively benign, except in a minority of cases. Such individuals may have a susceptibility to depression that manifests itself under certain conductive physiological conditions.