Adaptive actions as a mechanism of change in transdiagnostic internet-delivered cognitive behavioral therapy: Comparison with homework engagement

Adaptive actions have been identified as potential mechanisms of change in transdiagnostic internet-delivered cognitive behavioral therapy (ICBT), but their role relative to homework engagement remains unclear. This study examined whether changes in adaptive actions are maintained at follow-up, their relationship with homework engagement, their individual and joint prediction of diverse treatment outcomes, and their role as mediators and in reciprocal relationships with outcomes. Adults (<i>N</i> = 625) received a transdiagnostic ICBT program in routine care. Outcomes included depression, generalized anxiety, posttraumatic stress, panic, social anxiety, insomnia, functional impairment, and wellbeing. Adaptive actions were assessed with the Things You Do Questionnaire-15 Item (TYDQ-15) and homework engagement with the Homework Reflection Questionnaire (HWRQ). TYDQ-15 scores improved from pre- to post-treatment and were maintained at follow-up. Although correlated, mid-treatment TYDQ-15 scores more consistently predicted outcomes than homework engagement and partially mediated changes across all assessed outcomes. Reciprocal analyses revealed bidirectional relationships between adaptive actions and anxiety and wellbeing, and partially bidirectional associations with depression. Overall, mid-treatment adaptive actions emerged as a stronger and more consistent mechanism of change than homework engagement across diverse outcomes. Findings underscore the importance of research on the benefits of encouraging adaptive actions early in treatment.