• Electroencephalographic (EEG) sleep patterns were examined in nine unmedicated patients meeting DSM-III-R criteria for a current manic episode (four men and five women) for two to four consecutive nights. Compared with age- and sex-matched normal control subjects, manic patients exhibited significantly decreased total recording period, decreased time spent asleep, increased time awake in the last two hours of recording, shortened rapid eye movement (REM) latency, increased REM activity, and increased REM density. These results suggest that mania is associated with marked disturbances of sleep continuity and REM measures. Sleep continuity and REM sleep abnormalities of a similar nature and degree have been reported in major depression and psychotic depression. Thus, it is possible that various forms of affective disorders and psychotic disorders have pathophysiologic mechanisms in common.