EEG sleep profiles and recurrent depression.

Earlier investigations have suggested that electroencephalographic (EEG) sleep may be altered as a function of the duration of an episode of depression. We compared the EEG sleep profiles in a group of recurrent depressives who had been depressed for less than 6 weeks with their sleep profiles as measured during their previous episode of depression. Findings in this sample of 32 patients point to the presence of specific rapid eye movement (REM) sleep abnormalities as being more pronounced earlier in the course of a depressive episode. Changes in REM latency and REM activity were also reflected in reductions in EEG spectral power in almost all bandwidths during the first REM period of the recurrent episode. These results are not easily explainable on the basis of traditional measures of clinical severity or the number of episodes.