The Association Between Psychological Flexibility and Mindfulness: A Meta-Analytic Review.

Psychological flexibility and mindfulness are core constructs in contemporary models of adaptive functioning and clinical intervention. Although these constructs are conceptually linked, the empirical strength and consistency of their association remain unclear. This study presents the first meta-analytic review examining the correlation between psychological flexibility and mindfulness across published studies. A systematic literature search identified 45 eligible studies comprising a total of 16,316 participants. Effect sizes were calculated as Pearson's r and transformed into Fisher's z for analysis. Random-effects models were estimated using restricted maximum likelihood (REML). Between-study heterogeneity was evaluated using Q, I2, and τ2 statistics. Moderator analyses tested whether study characteristics (sample type, mean age, year of publication, sample size) and measurement features (type of psychological flexibility and mindfulness instrument, number of items) explained heterogeneity. Publication bias was assessed via funnel plots, regression tests, and the trim-and-fill method. The overall pooled correlation between psychological flexibility and mindfulness was significant (r = .44, 95% CI [.41, .53], p < .0001). Substantial heterogeneity was observed (I2 = 92.6%), warranting moderation analyses. Measurement-level moderators (type of psychological flexibility scale, number of items) significantly influenced effect sizes, whereas sample type, age, year, and sample size did not. Subgroup analyses revealed stronger correlations for AAQ-16 and AAO-II compared to other measures, and for FFMQ relative to MAAS. Publication bias analyses indicated no evidence of missing studies, and the trim-and-fill procedure confirmed the robustness of results (r = .44). Psychological flexibility and mindfulness demonstrate a robust positive association across diverse populations and instruments. However, the magnitude of this relationship varies by measurement tools, underscoring the importance of construct operationalization in future research. These findings highlight the interdependence of psychological flexibility and mindfulness within contemporary process-based models of adaptive functioning and suggest that interventions targeting one construct may enhance the other.