Effectiveness of psychological interventions to decrease cognitive fusion in patients with chronic pain: A systematic review and meta-analysis

Objective: While there is sufficient evidence of Acceptance and Commitment Therapy's effectiveness in allowing patients to deal with chronic pain, the effectiveness in cognitive fusion, one of the six core components of the Psychology Flexibility Model, has yet to be established. The aim of this article is to assess whether psychological interventions decrease cognitive fusion. Methods: The Web of Science, SCOPUS, Medline, and PsycINFO databases were searched for primary studies up to June 2024. Studies with a cognitive fusion measure in which chronic pain patients received a psychological intervention were included. A methodological quality scale was applied to the selected studies and the average effect sizes (Hedges g) were calculated. Results: This review included 18 articles with 24 studies (19 pre-post/follow-up studies and five randomized control trials). Cognitive fusion decreased significantly after the intervention. The effect sizes were small/medium at post-test, g = -0.39, p < .001, 95% CI [-0.52, -0.26]; and medium at long-term follow-up, g = -0.55, p < .001, 95% CI [−0.74, -0.36]. A similar tendency was found for studies with RCTs at post-test, g = -0.61, p = .006, 95% CI [−1.05, -0.17], short-term follow-up, g = -0.79, p < .001, 95% CI [−1.18, -0.40] and long-term follow-up, g = -0.58, p = .003, 95% CI [-0.95, -0.20]). Moderator variables such as unemployment, gender, pain intensity, level of depression before the intervention, and duration and intervention modality were identified. Conclusion: Psychological interventions tended to decrease cognitive fusion in chronic pain patients. Nonetheless, more clinical trials are needed to establish the role of cognitive fusion in psychological flexibility.