Reductions in experiential avoidance as a mediator of change in symptom outcome and quality of life in acceptance-based behavior therapy and applied relaxation for generalized anxiety disorder.

As a field, we lack information about specific mechanisms that are responsible for changes that occur over the course of treatments for anxiety disorders (Kazdin, 2007). Identifying these mechanisms would help streamline evidence-based approaches, increase treatment response rates, and aid in the dissemination and implementation of evidence-based approaches in diverse contexts. The current study examined reductions in experiential avoidance (EA; Hayes, Wilson, Gifford, Follette, & Strosahl, 1996), attempts to control or eliminate distressing internal experiences, regardless of behavioral consequences, as a potential mechanism of change in participants with a principal diagnosis of generalized anxiety disorder (GAD) receiving either acceptance-based behavior therapy (ABBT) or applied relaxation (AR). Participants' EA scores across treatment on the Acceptance and Action Questionnaire (AAQ) were used to calculate slopes, which were used as predictors in a series of linear regressions. Greater change in EA across treatment significantly predicted change in worry (PSWQ) and quality of life (QOLI) across both treatments. These results contribute to the body of literature on common mechanisms of change across traditional CBTs and mindfulness and acceptance-based approaches.