It's all about the process: Examining the convergent validity, conceptual coverage, unique predictive validity, and clinical utility of ACT process measures

Abstract

The Acceptance and Commitment Therapy (ACT) literature now offers a range of process measures, including: the Acceptance and Action Questionnaire-II (AAQ-II), the Open and Engaged State Questionnaire (OESQ), the Comprehensive Assessment of ACT Processes (CompACT), and the Multidimensional Psychological Flexibility Inventory (MPFI). The current study sought to directly compare and contrast the information provided by those scales: (1) in a sample of 2,385 online respondents (67% female, 85% Caucasian, M = 33yo) and (2) in a case study of a client receiving ACT for a depressive disorder. Quantitative results revealed that all of the flexibility scales were strongly linked to wellbeing whereas the inflexibility scales were strongly linked to psychological distress. The results further highlighted that newer multidimensional scales (the 3-dimension CompACT, the 12-dimension MPFI) offered greater insights into current functioning, often doubling the amount of variance explained by the AAQ-II alone. Both the quantitative analyses and the clinical case study demonstrate the more nuanced and clinically meaningful patterns that emerge when multiple dimensions of flexibility and inflexibility are tracked. In particular, the results suggested the MPFI (and the online MindFlex Assessment System that makes the MPFI easy to administer and interpret) offers researchers and clinicians the most conceptually comprehensive scale to assess the dimensions of the Hexaflex model. Implications for clinical research and practice are discussed.