Exploring the underlying mechanisms of Acceptance and Commitment Therapy

Literature review: Mediation studies evidence the mechanisms by which interventions produce clinical outcomes. Whilst consistent positive mediation results have been reported for the processes that compromise psychological flexibility (the model that underpins Acceptance and Commitment Therapy [ACT]), studies were limited in terms of study quality and scope. The present review aimed to update and extend the field by systematically collating, synthesising, and quality assessing ACT mediation studies. Results were consistent with the psychological flexibility model, however the studies reviewed were limited with regards to their quality and were focussed on a small number of putative processes. This review provides further support for the use of ACT. However, further research is required that addresses identified methodological limitations and increases the scope of ACT-focussed mediation studies.

Empirical research: In spite of claims that self-as-context is a key component within the psychological flexibility model of ACT, it has never been tested in a clinic-based component analyses. The present study aimed to assess the feasibility of conducting a large-scale dismantling component study of ACT focusing on the efficacy of self-as-context. Ten patients with long-term health conditions (LTCs) completed therapy involving either (1) Full-ACT or (2) ACT minus self-as-context (ACT-SAC). Significant improvements in psychological flexibility, decentring, functioning and depression were found for Full-ACT. Small effect sizes between study arms were found with regards to change scores on measures of functioning and depression. The adverse event rate was low. Overall, findings suggest that a large-scale trial would be safe and feasible. However measurement issues need attention and adverse events continued to be monitored.