The timing of sleep in depression: theoretical considerations.

Endogenously depressed subjects frequently show severe sleep problems. In this article sleep time in depression is discussed in relation to a recently developed model for sleep timing in healthy subjects. In terms of the model, two parameter sets survive a qualitative comparison with the empirical data. These are a deficient increase of sleep need (process S) and, alternatively, an increased amplitude of random fluctuations in the wake threshold (process C). Distinct predictions based on these alternatives are discussed.