[A review of sleep disorders in depression]

The main aims of this study are, on the one hand, to report on the current state of the art in research into the characteristics of sleep in depression and, on the other hand, to analyse the theoretical and practical implications of these results.

We review the main findings regarding the sleep disorders linked with depression and offer data about the sensitivity and specificity of these measures. The aetiopathogenic meaning of these sleep disorders is also analysed and finally we present some of the principal theoretical models put forward to explain these data.

A number of studies have observed significant alterations in electroencephalographic patterns during sleep in subjects with depression. Some of the most commonly mentioned findings involve disorders affecting the continuity and duration of sleep, a reduction of phases 3 and 4 of sleep, lowered latency in REM (rapid eye movements) sleep, and a longer and more intense first period of REM. This technique is presently of limited use as a diagnostic tool in depression. The pathophysiological mechanisms governing sleep disorders in depression are not yet known, but sleep studies still play an important role in research into depression, especially in areas concerning the prediction of responses to treatment, the prognosis of relapses, longitudinal results, familial studies and in research into aetiological models