Acceptance as a Mediator for Change in Acceptance and Commitment Therapy for Persons with Chronic Pain?

The aim of the present study is to investigate acceptance as a mediator in acceptance and commitment therapy (ACT), a third wave CBT intervention, for chronic pain. A bootstrapped cross product of coefficients approach was used on data from a previously published RCT evaluating ACT for chronic pain. To address the specificity of acceptance as a mediator, anxiety and depression were also tested as mediators. Outcome variables were satisfaction with life and physical functioning. Two change scores, pre-assessment to 6-month follow-up (n = 53) and pre-assessment to 12-month follow-up (n = 32), were used. Acceptance was found to mediate the effect of treatment on change in physical functioning from pre-assessment to follow-up at 6 months. Further, a trend was shown from pre-assessment to follow-up at 12 months. No indirect effect of treatment via acceptance was found for change in satisfaction with life. This study adds to a small but growing body of research using mediation analysis to investigate mediating factors in the treatment of chronic pain. In summary, the results suggest that acceptance may have a mediating effect on change in physical functioning in ACT for persons with chronic pain. However, given the small sample size of the study, these findings need to be replicated.