Effectiveness of the mindfulness-acceptance-commitment approach: a meta-analysis

The presented study evaluates the evidence base underpinning the use of the Mindfulness-Acceptance-Commitment approach (MAC) in applied sport psychology. To assess the effectiveness of the MAC protocol on improving mindfulness and psychological flexibility, and on enhancing sport performance and well-being among athletes, we used Robust Bayesian Meta-Analysis with Publication Selection Model-Averaging (RoBMA(PSMA)). In total, there were eleven controlled trials included in the meta-analysis. Results of the RoBMA(PSMA) show: a moderate model-averaged effect size estimate for developing mindfulness with strong evidence (g = 0.64, 95% CI 0.00-0.91, BFes = 25.35); a small model-averaged effect size estimate for experiential acceptance with anecdotal evidence (g = 0.36, 95% CI 0.00-0.92, BFes = 2.32); and a small model-averaged effect size estimate for improving sport performance with moderate evidence (g = 0.37, 95% CI 0.00-0.79, BFes = 3.27). Only one study assessed the effectiveness of the MAC protocol on well-being and averaged effect sizes ranged from 0.01 to 0.82. Based on the results of the meta-analysis, the Mindfulness-Acceptance-Commitment protocol can be effective in improving mindfulness. In addition, results suggest that the MAC protocol might be effective in improving sport performance. Currently available trials, however, do not provide sufficient evidence supporting the MAC protocol's effectiveness in developing psychological flexibility, experiential acceptance, and promoting well-being among athletes.