The association of a constellation of sleep disturbances in adults with major depressive episodes is perhaps the most robust and widely replicated abnormality in psychobiological studies of psychiatric disorders. Reduced sleep efficiency, deficits of slow wave sleep (SWS), reduced latency to the first rapid eye movement (REM) period, an increase of REM sleep time, and increased density of rapid eye movements (REMD) during REM sleep are strongly associated with depressive illness in most samples (Benca, Obermeyer, Thisted, & Gillin, 1992). Studies of children, adolescents, and young adults with major depressive episodes find similar sleep disruptions, although only partially expressed relative to findings in adults. As Table 15.1 summarizes, certain studies of adolescents with major depression have reported increased REM density, reduced sleep latency, increased time to sleep onset, and increased arousals, whereas others have found mixed results or no differences with nondepressed controls. Even in adults, the specificity of the association of disturbed sleep parameters with the state of depression has been questioned (Benca, Obermeyer, Thisted, & Gillin, 1992). In general, however, the changes in sleep macroarchitecture have been strongly connected to core features of depressive illness and likely parallel aspects of the underlying pathophysiology of severe depression.
More controversial have been claims that certain components of the depression-related sleep disturbances may point toward trait characteristics relating to vulnerability for depression in individuals.