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BackgroundThere is a diagnostic overlap between the clinical presentations of both major depressive disorder (MDD) and somatoform disorder (SD). Similar to MDD patients, SD patients usually have a disturbed sleep pattern. AimThe aim of this study was to assess the sleep profile of SD patients and compare it with that of MDD patients using sleep as a biological marker. MethodsWe investigated the sleep profile of 40 SD patients, in comparison with 40 MDD patients, and 40 healthy controls, by polysomnographic recordings of their sleep after a subjective assessment using an SCID1 Questionnaire, the Taylor Anxiety scale, the Beck Depression Inventory, the Toronto Alexithymia scale, and finally a sleep questionnaire. ResultsBoth MDD and SD patients had, in comparison with healthy controls, significantly decreased sleep efficiency, increased sleep latency and arousal index, increased stage 1 non rapid eye movement sleep, decreased stages 3 and 4 non rapid eye movement sleep, and thus decreased slow wave sleep, besides increased slow wave sleep latency. In addition, they had increased rapid eye movement (REM) percentage, first REM duration, and decreased REM latency. ConclusionAlthough not identical, the similar changes in the sleep patterns in both SD and MDD may suggest a common or a shared biological basis for both disorders.