Latencies of REM sleep and awakening in major depression: possible indicators of cholinergic activity

REM latency and awakening latency were analyzed in a sample of 26 major depressive inpatients and 8 male controls recorded for two consecutive nights. A significant inverse relationship appeared between REM latency and awakening latency in depressed patients. The relationship was more marked in male than in female patients. No significant correlation between REM latency and awakening latency was observed in male healthy volunteers. The hypothetical cholinergic supersensitivity in major depression is proposed to explain the present relationship. These results suggest that awakening latency might also be taken into account in the evaluation of sleep disturbances in depressive illness.