Acceptance and mindfulness interventions may improve psychological flexibility in chronic pain

Acceptance, a core dimension of psychological flexibility, showed consistent improvements across all time points (g=0.41–0.77). However, effects on committed action and values dimensions were not statistically significant. Moderator analyses revealed larger improvements when interventions were compared with inactive control groups, delivered by psychologists, or implemented as stand-alone programs rather than combined with other treatments. A major limitation is that most included trials carried a high risk of bias, and the overall certainty of evidence was rated low to very low due to heterogeneity in study designs and outcome measures. The authors note that more rigorous, well-designed trials are needed to clarify which dimensions of psychological flexibility respond most to these interventions and in which patient subgroups effects are largest.

The effect sizes for global psychological flexibility (0.35–0.69) are small to moderate—meaningful but not transformative on their own. Acceptance improvements (0.41–0.77) were more consistent and robust than improvements in other dimensions like committed action (non-significant) and values clarification (non-significant), suggesting the interventions work partly by helping people tolerate rather than eliminate pain-related thoughts and sensations. The heterogeneity across trials was substantial, reflecting differences in intervention duration, delivery mode, and control comparisons; effects were larger against inactive controls than active controls, which is typical in psychological research and suggests some expectancy effects. Interestingly, stand-alone programs outperformed combined interventions, hinting that layering multiple treatments may dilute focus. The low certainty rating reflects not just high bias risk but also small sample sizes in many trials, limited long-term follow-up, and inconsistency in how psychological flexibility was measured across studies.