Insomnia and depression: a multifaceted interplay.

Historically, insomnia has been viewed as a symptom of depressive illness that is expected to resolve with adequate treatment of the depressive disorder. This article reviews the evidence that increasingly challenges this simplistic view and summarizes research demonstrating the multifaceted interplay between insomnia and depression. It discusses the prevalence, clinical significance, and time course of insomnia, distinguishing between poor sleep and an insomnia disorder. The article also discusses abnormalities in sleep architecture in major depressive disorder and theories about the pathways connecting sleep and depression. It concludes with a discussion of issues related to treatment, including the effects of antidepressants on sleep and new evidence of the utility of adding an insomnia-specific therapy for improved management of depressed patients with comorbid insomnia.