Pathological and therapeutic consequences of sleep loss: a review.

Until recently sleep deprivation has been studied from the point of view of determining whether or not it produces deleterious effects. Evidence, however, has begun to accumulate indicating that both REM deprivation and single night sleep deprivation may have antidepressant effects. Although beneficial effects are found primarily in endogenously depressed patients, variable results have been obtained in both "endogenous" and "reactive" depressions, suggesting that these diagnostic categories include biologically heterogeneous populations.