Frequency analysis of the sleep EEG in depression.

Eight patients with major depressive disorder (seven bipolar and one unipolar) and matched controls had sleep studies, on which frequency analysis of the electroencephalogram (EEG) was performed. Total sleep and sleep efficiency were decreased in the patients, but there was no significant difference in rapid eye movement (REM) latency between the two groups. Frequency analysis revealed no group differences in power in the delta band (0.23-2.5 Hz) or the whole EEG spectrum (0.23-25 Hz). These findings suggest that mean REM latencies are not always shorter in major depression. The results are discussed in light of a previous report of decreased delta energy in the sleep EEG of unipolar patients.