Examining adherence and engagement variables as predictors of change in a digital acceptance and commitment therapy intervention for adults with chronic health conditions

Digital mental health interventions (DMHIs) are a promising resource for adults with chronic health conditions (CHCs). However, DMHI adherence is a challenge, with ongoing questions about how best to characterize and address the multifaceted features of engagement. This secondary exploratory analysis sought to characterize DMHI engagement variables including session completion, engagement in interactive exercises, time in sessions, and self-reported completion of homework assignments and to test which engagement variables predicted improvements in outcomes. A sample of 50 adults with a CHC randomized to an acceptance and commitment therapy-based DMHI were examined in this secondary analysis. Although adherence to DMHI sessions was only moderate (<i>M =</i> 4.04 sessions completed of 6), other engagement variables in sessions that participants completed were high. Time in sessions and homework completion were the most consistent predictors of improvements over time, especially for changes from baseline to one-month follow-up, such that only those highly engaged improved on well-being, mental health outcomes, and psychological flexibility. Session completion was the least consistent predictor of changes in outcomes. Overall, results suggest that it may be more important how users engage in DMHIs than the number of sessions completed, highlighting the importance of examining and addressing multiple features of engagement.