The significance of sleep physiological disturbances in depression.

Since the discovery of the antidepressant effects of interventions in the sleep-wake cycle, a number of hypotheses have emerged according to which disturbances in sleep physiology are not merely expressions but essential components of the pathophysiology of depression. Three hypotheses are presented, the "Phase-advance", the "S-deficiency" and the "ACh-hypersensitivity" hypotheses. They explain the therapeutic effects of total, partial and selective sleep deprivation as consequences of the normalization of disturbed sleep regulation. The question is dealt with whether there are indications that the hypothesized sleep regulatory disturbances exist and whether there is a relationship between the effects of sleep deprivation on sleep regulation and clinical state. None of the hypotheses is totally supported, none can be fully rejected.