The moderators of treatment response in acceptance and commitment therapy for physical and mental health conditions: a systematic review

Abstract

Acceptance and commitment therapy (ACT) has been shown to be effective for various physical and mental health conditions. In response to the need for personalised treatment, identifying the moderators of treatment response might help in the recognition of clients who will benefit the most from ACT. However, there is currently no review that synthesises these moderators. This systematic review aimed to bring together the moderators of treatment response in ACT from across a range of physical and mental health conditions. Embase, PsychINFO, Web of Science and PubMed were searched in March 2020. Randomised controlled trials, non-randomised controlled trials and observational studies were screened. Any studies that reported moderators of ACT with participants aged ≥18 years who had any mental health or physical condition were included. Fourteen studies met the inclusion criteria and were included in the review. These studies were critically appraised with respect to risk-of-bias, quality of the moderation analysis and intervention quality. Numerous moderators were reported across six mental health and physical conditions. The majority of studies reported non-significant results in relation to moderators of treatment outcomes. However, a high baseline of psychological inflexibility showed inconsistent findings across studies which suggest the need of future research in this area. Comorbid mood disorder, age and symptoms severity at baseline showed also some inconsistent results; however, in the majority of conditions, neither seemed to affect the response to ACT. Other reported moderators were either shown to be inconsistent across a limited number of trials or were reported only by a single study. Overall, this review did not find robust evidence for moderators of treatment response to ACT that could support an understanding of for ‘whom’ and ‘under what circumstances’ ACT works best. This was due to heterogeneity across the included studies, methodological limitations of the studies, and the limited number of trials relevant to each condition. Therefore, any moderators that have been identified should be interpreted with caution.