Electroencephalographic sleep profiles in single-episode and recurrent unipolar forms of major depression: I. Comparison during acute depressive states.

The current study was conducted to examine if recurrent depression is associated with more severe disturbances of all-night EEG sleep profiles than single-episode depressions. Unmedicated sex- and age-matched groups of 22 single-episode (SE) and 44 recurrent unipolar (RU) outpatients with DSM-III-R/SADS/RDC major depression underwent 2 consecutive nights of EEG sleep recording. Multivariate analyses of covariance (MANCOVAs) and/or analyses of covariance (ANCOVAs) were performed on six sets of sleep measures. Recurrent unipolar depression was associated with significantly increased phasic REM sleep, as well as increased REM counts on the second night of study. Recurrent depression also was associated with significantly poorer sleep efficiency, although the groups did not show consistent differences in sleep architecture or slow-wave sleep. Our findings generally support the hypothesis that recurrent depression is associated with a more severe neurophysiologic substrate than phenotypically similar SE cases. Results are, for the most part, compatible with Post's (1992) model of illness progression, particularly with respect to greater disturbances of state-dependent sleep abnormalities in the RU cases. Longitudinal studies are needed to confirm the evolution of such changes prospectively.