In plain language
For decades, clinical research has focused on testing whole therapy packages against each other. That approach can tell us a therapy works, but not why it works — which ingredients are active, which are inert, and how different therapies overlap. This book chapter takes the alternative route: it examines the processes of change in Acceptance and Commitment Therapy (ACT), asking whether ACT works in the way its theory predicts — by increasing psychological flexibility, the ability to accept inner experience, defuse from unhelpful thoughts, and act in line with one’s values.
The authors reviewed the mediational evidence across more than 50 studies — at the time, more mediational research than perhaps any other form of psychotherapy had inspired. The evidence indicated that ACT improves three markers of psychological flexibility: it reduces the believability of dysfunctional thoughts, increases acceptance of private experience, and reduces the belief that private experiences are barriers to action. Importantly, several lines of evidence suggested that changes in flexibility come before changes in symptoms, so flexibility is not merely a by-product of feeling better.
The chapter also shows that ACT’s processes are distinctive: studies comparing ACT with cognitive therapy and other CBT variants found that psychological flexibility mediated ACT outcomes but not the outcomes of the comparison treatments. The authors close by noting that existing measures capture markers of flexibility rather than flexible behavior itself, and call for more direct measures and for research on the distinctiveness of the six “hexaflex” processes.
Key findings
- Over 50 mediational studies of ACT were identified and reviewed, many completed in the five years before publication.
- ACT was found to improve three markers of psychological flexibility: reduced believability of dysfunctional thoughts, greater acceptance of private experience, and reduced belief that private experience blocks valued action.
- Most intervention studies showed that ACT produced correlated changes in psychological flexibility and clinical outcomes across a wide variety of populations and symptoms.
- Several ACT trials showed changes in psychological flexibility occurring before changes in symptoms, and longitudinal research showed flexibility predicting future mental health and workplace behavior controlling for baseline levels.
- Comparative studies (e.g., ACT vs. cognitive therapy and stress inoculation training) indicated that psychological flexibility was the primary mediator in ACT conditions but did not mediate outcomes of the comparison therapies, supporting distinct processes of change.
- The authors concluded that no existing measure directly assessed psychological flexibility itself — the tendency to persist or change behavior as the situation affords — and called for more direct measurement.
How to cite
APA
Ciarrochi, J., Bilich, L., & Godsell, C. (2010). Psychological flexibility as a mechanism of change in Acceptance and Commitment Therapy. In R. Baer (Ed.), Assessing mindfulness and acceptance: Illuminating the processes of change (pp. 51–76). New Harbinger Publications.
BibTeX
@incollection{ciarrochi2010psychological,
title = {Psychological flexibility as a mechanism of change in Acceptance and Commitment Therapy},
author = {Ciarrochi, Joseph and Bilich, Linda and Godsell, Clair},
booktitle = {Assessing Mindfulness and Acceptance: Illuminating the Processes of Change},
editor = {Baer, Ruth},
pages = {51--76},
year = {2010},
publisher = {New Harbinger Publications},
address = {Oakland, CA}
}
Related work
- All publications by Joseph Ciarrochi (searchable, with free PDFs)
- Process-Based Therapy & Idionomic Analysis
Author: Joseph Ciarrochi (ORCID 0000-0003-0471-8100). Free copy hosted with permission for scholarly use. Please cite the published version.