Effectiveness of guided digital CBT-I: a reflection on active control conditions, intervention engagement, and circadian components

Dear Editor, We received a reaction to our randomized controlled trial which was recently published at SLEEP [1]. We would like to thank the authors for the compliments on the design and execution of our study. We appreciate your thoughtful engagement with our study and would like to reflect and clarify on some of your mentioned aspects regarding the study design and interpretation. First, regarding the active nature of the control condition, we agree that it incorporated several active elements, including sleep hygiene, circadian-related health information, information on stimulus control, and self-monitoring through the sleep and light exposure diary. As you noted, this design choice has likely contributed to the within-group improvements in the control condition. We explicitly mention this overlap in the discussion section [2]. However, it is also important to emphasize that the broader scientific literature consistently demonstrates that sleep hygiene education/psychoeducation is generally less effective as a standalone intervention for insomnia than multi-component cognitive-behavioral therapy for insomnia (CBT-I) programs [3]. Comparing individual CBT-I components, sleep hygiene is considered less beneficial than other components such as sleep restriction, stimulus control and cognitive restructuring [4]. However, our findings suggest that high-quality psychoeducation can be beneficial for university students, as the within-group effect size of the control condition is larger than what would be expected from non-specific effects alone.