Primary Analysis.
RECRUITMENT
ITT analyses included all randomized participants, irrespective of the amount of therapy received, using Stata version 15. IDMC recommended three informative contrasts for future clinical service design prioritized to minimize false positive results. The sequence was: (1) determine any difference in the therapist-supported arms (Group vs One-to-One) and if no difference then arms are combined, (2) test whether independent CR improved the primary outcome (Independent vs TAU), and finally (3) a comparison of the combined therapist arms with TAU to consider the overall treatment effect. These pre-specified analyses (see A linear mixed model estimated the mean weighted GAS T-score difference between arms at 15 weeks. Independent variables were treatment arm, time (post therapy or follow-up), time by treatment arm interaction, recruitment period (pre- or post-interim analysis), baseline GAS T-score, recruitment site, and a random patient-specific intercept. A dummy indicator for baseline missingnessSensitivity analyses assessed, by simulation, the effect of closing arms following the interim analysis, under 2 scenarios (1) no treatment difference and (2) naïve effect estimates for the primary outcome. Additional analyses examined: (1) assumed lack of clustering by site/group, (2) missing at random assumption, and (3) effect of noncompliance to visit windows (see An additional analysis estimated the effect of receiving treatment (CR hours) on the primary outcome. As those who received more CR were likely to be different from those who did little, we used random treatment assignment as an instrumental variable