Iranian Association for Intelligence and Talent Studies International Journal of Education and Cognitive Sciences 3041-8828 7 September 2026 2026 05 01 Meta-analysis of the Effectiveness of Mindfulness-Based Interventions on Rumination: A Systematic Review of Iranian Trials Meta-analysis of the Effectiveness of Mindfulness-Based Interventions on Rumination: A Systematic Review of Iranian Trials 1 12 10.61838/kman.ijecs.357 EN Journal Article 2025 12 03 <p>Rumination is generally defined as a process of repetitive thinking during which attentional and cognitive resources, as well as problem-solving abilities, are weakened, ultimately leading to threat and negative self-referentiality in an individual's behavior. This study aimed to determine the combined effect size of mindfulness-based interventions on reducing rumination and analyze its moderating factors, conducting a systematic meta-analysis on 40 randomized controlled trials published in Iran between 2009 and 2025 (with a total of 1471 participants). Using a random-effects model, a large and significant combined effect size was obtained (g = 1.21 with a 95% confidence interval), confirming the remarkable effectiveness of these interventions. Despite very high heterogeneity between studies, moderator analysis showed that effectiveness in clinical populations was significantly greater than in non-clinical populations. However, the type of assessment tool (RRS vs. other tools) and the number of intervention sessions (8 sessions vs. more) did not create a significant difference in effect size. The overall conclusion indicates that mindfulness-based therapies, especially for clinical populations, are an effective strategy for reducing rumination and provide strong empirical support for inclusion in treatment protocols for disorders such as depression and anxiety. Nevertheless, high heterogeneity and signs of publication bias emphasize the need for future research with direct comparative and long-term longitudinal designs to better understand optimal conditions and mechanisms of action.</p>