EEG sleep in young depressives: first and second night effects

The sleep electroencephalogram (EEG) of young, drug-free, recurrently depressed outpatients was analyzed for 2 nights and was compared to age-matched controls using a variety of standard and computerized measures of sleep activity. On the first night, young depressives showed significantly greater difficulty in falling asleep and decreased sleep efficiency. Sleep architecture differences between the young depressives and controls were highlighted by increased percentages of Stage 2 sleep and major decreases in Stages 3 and 4 (delta wave) sleep among the depressives, as indicated by either period analyses or spectral analysis. The greatest differences in delta wave activity during night 1 were found in the first two (non-rapid eye movement (NREM) periods as measured by period analysis (NREM period 1, p less than 0.04; NREM period 2, p less than 0.001--average delta wave count) or by spectral analysis for the first 100 min of sleep (0.5-2.0 Hz). In contrast to the NREM sleep findings, various REM variables, including REM latency did not significantly distinguish the two subject groups for either night 1 or 2. Stepwise discriminant analysis demonstrated that night 1 sleep latency and delta wave counts during the second NREM period correctly classified 100% of all 16 individuals studied. The only differences between the young depressed patients and controls that remained on night 2 were significant reductions in slow-wave sleep as quantified by the computerized methods. Taken together, these findings suggest that the EEG response of young outpatients to the first night's stay in a sleep laboratory may be a useful tool for the diagnosis of depression in this age group. In addition, the use of computerized methods in this study point to an underlying deficit in delta sleep waveforms as being a prominent feature of the sleep of young depressed subjects.