Mediators of cognitive-behavioral therapy for insomnia: a review of randomized controlled trials and secondary analysis studies.

The examination of treatment mechanisms in randomized controlled trials (RCTs) has considerable implications for research and clinical practice. Insomnia is a highly prevalent and distressing disorder, associated with many adverse outcomes. Although extensive work has focused on the cognitive-behavioral treatment of insomnia (CBT-I), few studies have directly examined the mechanisms of this intervention. CBT-I is a short-term, multi-component treatment that has demonstrated strong efficacy in treating insomnia. The purpose of the present study is: (a) to investigate if CBT-I works in accordance with its proposed mechanisms, and (b) to evaluate how the field is progressing in its understanding of these processes. This study comprehensively reviewed CBT-I RCTs for their inclusion of mediator variables. Secondary analysis studies were also surveyed for relevant mediator variables. Results demonstrated that 21 RCTs (39% of the total RCTs) and 11 secondary analysis studies examined at least one of the proposed mediators. Results of this review highlight that, although CBT-I appears to be targeting the hypothesized sleep processes, more research is needed to better understand whether CBT-I works in accordance with its theorized mechanisms. Inclusion of mediational analyses in future RCTs and secondary analysis studies would allow for further refinement of CBT-I and improved treatment outcomes.