Slow-wave activity during non-REM sleep in men with schizophrenia and major depressive disorders

Both major depressive disorders (MDD) and schizophrenia (SZ) have been associated with reductions in slow-wave (Stages 3 and 4) sleep, although these findings are controversial. The present study compared quantitative EEG measures of slow-wave activity (0.5-4 Hz) during non-REM (NREM) sleep among age-matched, symptomatic but unmedicated, depressed, schizophrenic and healthy control men (n=13/group). The amplitude of slow-wave activity (SWA) in the first NREM sleep period was significantly lower in both the MDD and SZ groups compared with controls. However, the time course of SWA, its accumulation and dissipation over all NREM sleep time, was abnormal in the MDD group but not in those with SZ. These findings suggest that the regulation of SWA is impaired in men with MDD but not in SZ. Thus, although those with SZ show reduced amplitude SWA in the first NREM period, there is no evidence that homeostatic regulation of SWA is impaired in this psychiatric group.