Significance of REM Sleep in Depression: Effects on Neurogenesis

Copyright: © 2012 Palagini L, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Disturbances of sleep are typical of depression and are observed in between 50% and 90% of depressed subjects [1]. Most patients with depression complain of insomnia and have well-described sleep disruptions, which belong to the core symptoms of the disorder [2]. Sleep disorders in depression have stimulated many sleep studies and for many decades sleep research has been a major pillar of neurobiological investigations into depression’s cause, onset and course. Since 1960s polysomnographic sleep research has demonstrated that besides disturbances of sleep continuity a constellation of sleep EEG changes is present in depression [3,4]. Especially Rapid Eye Movement activity has been the favorite focus of sleep EEG studies in depression and studies on its significance indicate that a strong link exists between dysregulation of REM sleep, REM latency, REM density, and the cause, onset and course of major depressive disorders. These alterations might act as trait dependent marker of depression and have been considered biological marker for depression. Especially shortened REM sleep Latency might be both a prodrome of major depressive episodes [2] and a consequence or complication of depression [2,5]. In fact REM alterations often persist beyond the clinical episode indicating heightened vulnerability to depressive relapse or recurrence, negative affecting treatment response independent of treatment method [2,6]. Moreover because the majority of antidepressant irrespective of their chemical class suppress REM sleep, it has been hypothesized that REM sleep suppression might be considered a key mechanism underlying treatment response and might be considered necessary if an antidepressant effect is obtained. Recently REM deregulations have been described to have a role in the production of the core symptoms of mood disorder contributing to the core features of cognitive distortion including self-worth [7] and to negative emotional memories consolidation. Studies have in fact demonstrated that there is a failure of sleep dependent emotional brain processing in REM sleep in depression which seems to support the development of clinical depression [8]. In addition, REM sleep is physiologically abnormal in persons at risk for depression. In fact several high risk studies including healthy relatives of patients with depression have demonstrated that REM sleep, particularly REM density changes, are present before the disorder’s onset and predict its development.