ACT: A Process-Based Therapy in Search of a Process.

A large array of randomized controlled trials and meta-analyses have determined the efficacy of Acceptance and Commitment Therapy (ACT). However, determining that ACT works does not tell us how it works. This is especially important to understand given the current emphasis on Process-Based Therapy, the promise of which is to identify manipulable causal mediators of change in psychotherapy, and how their effectiveness is moderated by individual contexts. This paper outlines four key areas of concern regarding ACT's status as a Process-Based Therapy. First, the relationship between ACT and Relational Frame Theory has been widely asserted but not yet properly substantiated. Second, most of the studies on ACT's core process of change, psychological flexibility, have used invalid measures. Third, while lots of research indicates means by which individuals can be helped to behave consistently with their values, there is virtually no research on how to help people effectively clarify their values in the first instance, or indeed, on an iterative basis. Finally, the philosophy underlying ACT permits a-moral instrumentalism, presenting several ethical challenges. We end by making several recommendations for coherent methodological, conceptual, and practical progress within ACT research and therapy.