[Sleep and depression (author's transl)]

This critical review of the literature concerns the electrophysiological studies of sleep applied to depressed patients. While the (phenomenological) studies confirm the actual sleep disturbances in most patients and at certain stages of the depressive episodes, the (parallelistic) studies failed to evidence any strict correlation between quantified sleep data and nosographical classifications of depressions. The reductionistic) studies, searching into sleep measurements indices of specific biochemical disturbances also lead to contradictory and questionable conclusions. The explanation of this negative assessment is not to be found in methodological deficiencies but must be searched at the level of the theoretical approach of the problem.