The timing of partial sleep deprivation in depression.

In 26 major depressed and 4 schizoaffective inpatients (according to the RDC) early and late partial sleep deprivation (PSD) were carried out. For most of the patients (N = 25) this was done in a balanced crossover design. Residual sleep, starting at 21:00 or 2:00 respectively, was recorded polygraphically. Total sleep time was held constant between the 2 conditions (168 +/- 46 min in early sleep, 173 +/- 28 min in late sleep). Mood ratings with 5 different measures on the 2 days following each PSD revealed significant therapeutic effects from both procedures with only minor differences between them. Thus, sleep reduction as such and not the time at which it takes place (first or second half of the night) appears to be the therapeutic agent in PSD.