The Scientific Status of Acceptance and Commitment Therapy: An Analysis From the Philosophy of Science.

How good is the science in the Acceptance and Commitment Therapy (ACT) program? This article examines ACT philosophy, theory, and research on five dimensions: (1) the quality of its meta-science; (2) the clarity of its constructs; (3) the psychometrics of its principal measures; (4) the adequacy of its account of values; and (5) the quality of its research. Significant problems are found in each dimension, and suggestions for improvements are offered. ACT aligns with a Machiavellianism that is problematic in accurately describing these commitments and constituting a meta-stance that permits problematic values to be embraced. Relatedly, there is evidence of a positive bias in ACT research that has been ignored methodologically and in summaries of ACT. These problems justify significant skepticism regarding any claims from the science associated with ACT. Avoiding questionable research practices, psychometrically problematic measures, and research designs that weaken valid causal inference is recommended. Finally, an increased commitment to open science, intellectual humility, and severe testing is recommended.