Investigating experiential avoidance as a mechanism of action in a mindfulness intervention

Mechanisms of change in psychotherapy must be empirically investigated to shed light on how particular therapies work, as well as common mechanisms that may be at work across modalities. The current study investigated a proposed mechanism of change in a mindfulness intervention; this proposed mechanism, experiential avoidance (EA), may function more broadly as a mediator of change across multiple therapies. The primary hypothesis was that gains in mindfulness over the course of Mindfulness-Based Stress Reduction (MBSR) would be associated with reductions in negative affect, and that changes in EA would mediate the relation between changes in mindfulness and negative affect. The role of EA in mediating the effect of mindfulness on positive affect, disability, and life satisfaction was also investigated. Participants (N = 106) completed questionnaires before and after an 8-week MBSR program. A subset of participants (n = 74) completed questionnaires at the mid-point of treatment, and recorded time spent on mindfulness practice and level of relaxation after homework completion. Mediation analyses were conducted in which relations between change in predictor (mindfulness), mediator (EA), and outcome measures over the course of the intervention were assessed using regression steps, followed by PRODCLIN. Participants reported significant improvements in mindfulness, reductions in EA and disability, and improved affect and life satisfaction from pre- to post-MBSR. The relation between increased mindfulness and reduced negative affect over the course of the intervention was partially mediated by reduced EA. No evidence was found for relaxation as an additional mediator of the relation between mindfulness and negative affect. The relation between increased mindfulness and positive affect over the course of the intervention was fully mediated by decreased behavioral avoidance. Reductions in behavioral avoidance also fully mediated the relation between increased mindfulness and reduced disability. The relation between increased mindfulness and increased life satisfaction was mediated by EA. More mindfulness practice was linked with greater positive affect; the relation between practice and positive affect was mediated by EA. This study offers support for EA as a mediator of the effect of mindfulness on multiple outcomes, while highlighting a mechanism of change that may pertain across psychotherapeutic modalities.