Competence and adherence in an acceptance and values-based intervention: Effects on treatment outcome and early changes in depression

Abstract Background The present study investigated competence and adherence in an acceptance- and values-based intervention and their impact on the outcomes of treatment and early changes in depression. Method A total of 74 sessions delivered by novice therapists (n = 37) were rated for overall competence and adherence to treatment manual, as well as for process-specific components of acceptance and commitment therapy (ACT) using the ACT Adherence Scale ( Plumb & Vilardaga, 2010 ). The relationships between (a) competence and adherence, (b) treatment outcome, and (c) early therapeutic changes among patients diagnosed with major depressive disorder (n = 37) were explored. Results Higher competence and better adherence to ACT were associated with larger overall changes in depressive symptoms (r = 0.37 and r = 0.39, respectively). Specifically, the more frequently and extensively the therapists addressed committed action during their intervention, the larger the overall changes in depression and psychological flexibility. The regression analyses suggested that close to 40% of variation in overall changes in depressive symptoms was explained by an early change in depressive symptoms and adherence to the ACT model, in which early change was the strongest predictor. When early change was not included in the regression model, both competence and adherence in ACT explained 13–14% of variation in overall changes in depression. Competence and adherence were not associated with overall change in psychological flexibility. Discussion The present study suggests that competence and adherence in ACT may be associated with favorable outcomes of treatment in depression. We call for further evidence and discussion about competence and adherence in process-based interventions.