Do Acceptance‐ and Mindfulness‐Based Interventions Improve Psychological Flexibility in People With Chronic Pain? A Systematic Review and Meta‐Analysis of Randomized Controlled Trials

Background: Acceptance- and mindfulness-based interventions are effective for improving pain-related outcomes, yet their effects on psychological flexibility have not been meta-analyzed. This systematic review and meta-analysis addressed this gap by comparing these interventions with control conditions on psychological flexibility and its core dimensions in adults with chronic pain.

Methods: Searches were conducted in PsycINFO, MEDLINE, Cochrane CENTRAL, Scopus and Web of Science from inception to May 2025. Sixty randomized controlled trials comprising 6692 participants were included. Meta-analyses were conducted for global psychological flexibility (k = 17), acceptance (k = 38), committed action (k = 4) and values (k = 4). Heterogeneity, risk of bias and certainty of evidence were assessed.

Results: Interventions significantly improved psychological flexibility at post-treatment, short-term (≤ 6 months) and long-term (> 6 months) follow-up (g = 0.35-0.69), and acceptance across all time points (g = 0.41-0.77). Effects for committed action and values were non-significant. Heterogeneity was substantial, most trials had a high risk of bias, and the certainty of evidence was low to very low. Moderator analyses indicated larger effects when interventions were compared with inactive controls, delivered by psychologists or implemented as stand-alone programs.

Conclusions: Evidence suggests that acceptance- and mindfulness-based interventions may improve global psychological flexibility and acceptance. However, the certainty of evidence was low to very low, and most included trials were at high risk of bias. More rigorous trials are needed to clarify effects across specific dimensions of psychological flexibility.

Significance: STATEMENT: This systematic review and meta-analysis provide the first comprehensive synthesis of the effects of acceptance- and mindfulness-based interventions on psychological flexibility in chronic pain. These findings show that these interventions improve psychological flexibility, particularly pain acceptance, supporting it as a clinically relevant treatment target.

Trial Registration: PROSPERO: CRD420251018441.