Fourteen patients with obsessive-compulsive disorder (OCD) were studied with all-night sleep EEG recordings. Nine of these patients reported abnormal sleep patterns before the polygraphic study. Analysis of the sleep records disclosed significantly decreased total sleep time with more awakenings, less stage 4 sleep, decreased rapid-eye-movement (REM) efficiency, and shortened REM latency compared ... [Show full abstract] with those of a group of age- and sex-matched normal subjects. These abnormalities generally resembled those of an age-matched group of depressed patients, although significant differences remained. These findings suggest that such sleep abnormalities as shortened REM latency may not be entirely specific for primary affective illness. They also point to a possible biological link between OCD and affective illness.