Abstract
Acceptance and commitment therapy (ACT) emphasizes a focus on theory-driven processes and mediating variables, a laudable approach. The implementation of this approach would be advanced by addressing five challenges, including (a) distinguishing ACT processes in measurement contexts, (b) developing and rigorously validating measures of ACT processes, (c) the wide use of psychometrically weaker ACT process measures and the more limited use of stronger measures in earlier work, (d) the inconsistency of past evidence that ACT processes are sensitive or specific to ACT or mediate ACT outcomes specifically, and (e) improving statistical power and transparency. Drawing on the existing literature, we characterize and provide evidence for each of these challenges. We then offer detailed recommendations for how to address each challenge in ongoing and future work. Given ACT's core focus on theorized processes, improving the measurement and evaluation of these processes would significantly advance the field's understanding of ACT.