Effectiveness of internet-based self-help cognitive behavioral therapy for insomnia (CBT-I) among community adults: A randomized controlled trial.

While research on internet-based Cognitive Behavioral Therapy for Insomnia (CBT-I) is growing, questions remain regarding its mechanisms and broader benefits beyond reducing insomnia. The present study aims to contribute to the literature by developing, implementing, and evaluating a new internet-based self-help CBT-I among community adults with mild-to-moderate insomnia in Hong Kong. Participants were randomly assigned to either a CBT-I intervention group (n = 179) or a waitlist control group (n = 179). Both groups completed questionnaire measures at baseline (T1), immediately after the intervention (T2), and 4 weeks post-intervention (T3). Compared to the control group, the intervention group demonstrated greater reductions in insomnia symptoms, sleep disturbance, pre-sleep arousal, maladaptive sleep hygiene practices, dysfunctional beliefs and attitudes about sleep, depressive and anxiety symptoms, cognitive impairments, and work and social difficulties, as well as greater improvements in well-being and health-related quality of life at both T2 and T3. The effect sizes of these changes ranged from small to medium. Mediation analyses further revealed that pre-sleep arousal significantly mediated the effects of the intervention on insomnia symptoms. Importantly, our findings demonstrate that internet-based self-help CBT-I effectively reduces insomnia severity, with pre-sleep arousal as a key mechanism, and yields broader benefits, such as alleviating affective symptoms and functional impairments and promoting health and wellness. Given its efficacy, accessibility, scalability, and cost-effectiveness, this intervention represents a promising first-line approach for managing insomnia in the community.