Chronic pain conditions are common and have a considerable impact on health and wellbeing. This impact can be reduced by cognitive behavioral therapy (CBT), the most commonly applied psychological approach to chronic pain. At the same time, CBT continues to develop, and now includes what is sometimes called "third wave" CBT. In this review, we examine the evidence for application of acceptance and commitment therapy (ACT), a principal example of this new wave or latest generation of treatment approaches, in people with chronic pain. We identified 25 randomized controlled trials of ACT for adults with chronic pain. Across the included trials, small to large effect sizes favoring ACT were reported for key outcomes including pain interference, disability, depression, and quality of life. Evidence from three studies provided some support for the cost effectiveness of ACT for chronic pain. Evidence also supported the mediating role of theoretically consistent processes of change (psychological flexibility) in relation to treatment outcomes. Investigation of moderators and predictors of outcomes was limited and inconsistent. In future, a greater focus on process based treatments is recommended. This should include continued identification of evidence based processes of change, and research methods more suited to understanding the experience and needs of individual people.
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