Insomnia as a transdiagnostic process in psychiatric disorders.

Insomnia is a major public health concern, and is highly comorbid with a broad range of psychiatric disorders. Although insomnia has historically been considered a symptom of other disorders, this perspective has shifted. Epidemiological and experimental studies suggest that insomnia is related to the onset and course of several psychiatric disorders. Furthermore, several randomized controlled trials show that cognitive behavioral therapy for insomnia delivered to individuals who meet diagnostic criteria for insomnia and another psychiatric disorder improves the insomnia as well as the symptoms of the comorbid psychiatric disorder. Taken together, these results encompassing a range of methodologies have provided encouraging evidence and point toward insomnia as a transdiagnostic process in psychiatric disorders.