The impact of module dosage on treatment response in a modular transdiagnostic intervention for sleep and circadian...

The efficacy of modular evidence-based psychological treatments is promising, yet variation in module delivery is understudied. This study evaluated module delivery of the Transdiagnostic Intervention for Sleep and Circadian Dysfunction (TranS-C) and its impact on patient outcomes. Adults (N = 108) with serious mental illness and sleep and circadian dysfunction treated in a community setting were randomized to receive TranS-C plus usual care, or 6 months of usual care followed by delayed treatment with TranS-C. Data from both conditions were combined to maximize power. These secondary analyses tested whether the "dosage" of module delivery (defined as the proportion of total sessions in which a module was delivered) predicted treatment response, measured as functional impairment, psychiatric symptoms, sleep and circadian dysfunction, and sleep health, at post-treatment and 6-month follow-up. Higher dosages of seven modules were associated with improvement in the outcome variables (βs = -0.11-0.44; ps = 0.000-0.030). Higher dosages of three modules were associated with a worsening of one or two outcome variables (βs = 0.22-0.29; ps = 0.001-0.043). Higher dosages of the remaining modules were not associated with outcomes. Although more evidence is needed, it may be wise to consider focusing provider trainings on ensuring fidelity to certain modules, given limited training time in community settings. ClinicalTrials.gov Identifier: NCT02469233, registered June 9, 2015.