Effect of insomnia treatments on depression: A systematic review and meta-analysis

Background: Insomnia is frequently co-morbid with depression, with a bidirectional relationship between these disorders. There is evidence that insomnia-specific interventions, such as cognitive behavioral therapy for insomnia, may lead to improvements in depression. The purpose of this systematic review and meta-analysis is to determine whether treatment of insomnia leads to improved depression outcomes in individuals with both insomnia and depression. Methods: We conduct a systematic review and meta-analysis to explore the effect of treatment for insomnia disorder on depression in patients with both disorders. Results: Three thousand eight hundred and fifteen studies were reviewed, and 23 studies met inclusion criteria. Although all of the studies suggested a positive clinical effect of insomnia treatment on depression outcomes, most of the results were not statistically significant. Although the interventions and populations were highly variable, the meta-analysis indicates moderate to large effect size (ES) improvement in depression as measured with the Hamilton Depression Rating Scale (ES = -1.29, 95% CI [-2.11, -0.47]) and Beck Depression Inventory (ES = -0.68, 95% CI [-1.29, -0.06]). Conclusions: These results support that treating insomnia in patients with depression has a positive effect on mood. Future trials are needed to identify the subtypes of patients whose depression improves during treatment with insomnia-specific interventions, and to identify the mechanisms by which treating insomnia improves mood.