The evidence base of sleep restriction therapy for treating insomnia disorder.

Sleep restriction therapy is routinely used within cognitive behavioral therapy to treat chronic insomnia. However, the efficacy for sleep restriction therapy as a standalone intervention has yet to be comprehensively reviewed. This review evaluates the evidence for the use of sleep restriction therapy in the treatment of chronic insomnia. The literature was searched using web-based databases, finding 1344 studies. Twenty-one were accessed in full (1323 were deemed irrelevant to this review). Nine were considered relevant and evaluated in relation to study design using a standardized study checklist and levels of evidence. Four trials met adequate methodological strength to examine the efficacy of therapy for chronic insomnia. Weighted effect sizes for self-reported sleep diary measures of sleep onset latency, wake time after sleep onset, and sleep efficiency were moderate-to-large after therapy. Total sleep time indicated a small improvement. Standalone sleep restriction therapy is efficacious for the treatment of chronic insomnia for sleep diary continuity variables. Studies are insufficient to evaluate the full impact on objective sleep variables. Measures of daytime functioning in response to therapy are lacking. Variability in the sleep restriction therapy implementation methods precludes any strong conclusions regarding the true impact of therapy. A future research agenda is outlined.