The Effect of Sleep Disturbances on Major Depressive Disorder.

Sleep disturbances not only commonly occur in major depressive disorder, but constitute one of the symptom criteria. Importantly, there is growing inference that sleep disturbances may be more than a symptomatic byproduct of depression; poor sleep may play a role in the development or clinical course of depression, or both. This article reviews the prevalence of the two major classes of sleep disorders, the insomnias and the sleep-disordered breathing disorders, as they pertain to depression. Beyond prevalence, the empirical evidence reviewed suggests that insomnia is a risk factor for depression and that obstructive sleep apnea (OSA) is highly associated with depression. Preliminary evidence indicates that OSA may also be a risk factor for this disorder. The implications of these findings for the treatment of sleep disturbances either prior to or in the context of depression are discussed.