Mindfulness-based stress reduction: A meta-analysis of psychological outcomes

Objective. Mindfulness-Based Stress Reduction is a group-administered intervention that has grown in popularity since its development as a treatment for adjustment to alleviation of chronic pain. Jon Kabat-Zinn developed MBSR (Kabat-Zinn, 1982) and its eight weekly classes typically include formal instruction, meditation, yoga/body movement, homework, and a day-long retreat. Results from individual studies tend to be positive but are not uniformly so, with significant variation in methodological quality among the investigations. The current study aimed to answer the question: When analyzing the highest quality studies of MBSR, does MBSR have a positive treatment effect on psychological outcomes?;Method. A systematic literature search identified 17 randomized controlled trials examining MBSR with a total of 831 subjects. Studies were coded independently by two coders, who reached consensus on all variables. A standardized mean difference score adjusted for sample size was calculated for each included study.;Results. When compared to wait list controls, MBSR had an estimated random-effects weighted average effect size of d=0.542 in psychological outcomes. When compared to a minimal treatment, the effect size was d=0.258. When compared to an active treatment condition, the effect size was d=-0.249. Sub-group analysis revealed moderate effects of MBSR on depression, anxiety, and distress and large effects for stress. Population and publication types moderated the effect size, while demographic characteristics (i.e., ethnicity, education, and gender) did not. Duval and Tweedie's trim and fill method (Duval & Tweedie, 2000) indicated publication bias was not present.;Conclusion. Results suggest that when MBSR is compared to waitlisted controls, MBSR is effective across a broad range of psychological outcome variables and particularly helpful for stress. Comparisons with other forms of treatment are less favorable for MBSR.