Chronic insomnia disorder affects up to 10% of the general population and 30% of those with mental disorders. Cognitive Behavioral Therapy for Insomnia (CBT-I) is the first-line treatment, but its implementation remains challenging. The SLEEPwindow intervention focuses on the behavioral module of CBT-I (bedtime restriction, stimulus control) and may be an effective, brief, and cost-effective standalone intervention for outpatients with chronic insomnia disorder. This study evaluates whether SLEEPwindow is non-inferior to full CBT-I.

This is a non-inferiority trial comparing CBT-I and the SLEEPwindow intervention. A total of 130 patients with chronic insomnia disorder will be randomized into two groups: CBT-I (six 90-minute group sessions) and SLEEPwindow (four 60-minute group sessions). CBT-I includes sleep education, stimulus control, cognitive therapy, relaxation, and bedtime restriction. SLEEPwindow focuses on the behavioral module of CBT-I (bedtime restriction and stimulus control), as a standalone intervention.

The primary outcome is the Insomnia Severity Index (ISI), measured at baseline, 6 weeks (T1), 3 months (T2), and 6 months (T3). Secondary outcomes include subjective sleep quality (sleep diaries), daytime sleepiness (Epworth Sleepiness Scale), sleep-related quality of life (Glasgow Sleep Impact Index), treatment adherence (actigraphy, sleep diaries), subjective treatment experience, and assessment of treatment costs. The primary hypothesis is that SLEEPwindow is non-inferior to CBT-I across time for improving insomnia severity. Non-inferiority will be defined as a difference of no more than 2 points on the ISI, assessed using a one-sided 97.5% confidence interval.

The primary hypothesis of this trial is that SLEEPwindow is non-inferior to full CBT-I. If confirmed, SLEEPwindow could become a more accessible and cost-effective treatment. The study will also provide insights into treatment mechanisms and implementation challenges.