Mediators of change in acceptance and commitment therapy for pediatric chronic pain.

Even though psychological interventions are well established in the treatment of pediatric chronic pain, there is a clear need for further development, especially with severely disabled patients. However, optimizing effectiveness in psychological treatments for pain requires clarification of the mechanisms of action. Studies addressing change processes are scarce, however, particularly in relation to pediatric chronic pain. Acceptance and Commitment Therapy (ACT), as an extension of traditional cognitive behavior therapy, is essentially aimed at improving functioning by increasing the ability to act effectively in the presence of pain and distress, that is, psychological flexibility. ACT has shown promising results for both adult and pediatric chronic pain. In the present study, the mediators of change in an ACT-oriented treatment for pediatric chronic pain were examined using a bootstrapped cross product of coefficients approach. Pain interference and depression were used as outcome variables. Six different variables relevant to theories underlying ACT and cognitive behavior therapy were included in the analyses as possible mediators of change: pain impairment beliefs, pain reactivity, self-efficacy, kinesiophobia, catastrophizing, and pain intensity. Results illustrated that pain impairment beliefs and pain reactivity were the only variables that significantly mediated the differential effects of treatment on outcomes at follow-up. Also, these 2 mediators were shown to independently predict effects in outcome variables at follow-up while controlling for earlier effects in outcome, but only for the ACT condition. Although tentative, the pattern of results suggests that variables consistent with psychological flexibility mediate the effects of ACT-based interventions to improve functioning in patients with chronic debilitating pain.