Mindfulness-based stress reduction for healthy individuals: A meta-analysis.

BACKGROUND An increasing number of mindfulness-based stress reduction (MBSR) studies are being conducted with nonclinical populations, but very little is known about their effectiveness. OBJECTIVE To evaluate the efficacy, mechanisms of actions, and moderators of MBSR for nonclinical populations. DATA SOURCES A systematic review of studies published in English journals in Medline, CINAHL or Alt HealthWatch from the first available date until September 19, 2014. STUDY SELECTION Any quantitative study that used MBSR as an intervention, that was conducted with healthy adults, and that investigated stress or anxiety. RESULTS A total of 29 studies (n=2668) were included. Effect-size estimates suggested that MBSR is moderately effective in pre-post analyses (n=26; Hedge's g=.55; 95% CI [.44, .66], p<.00001) and in between group analyses (n=18; Hedge's g=.53; 95% CI [.41, .64], p<.00001). The obtained results were maintained at an average of 19 weeks of follow-up. Results suggested large effects on stress, moderate effects on anxiety, depression, distress, and quality of life, and small effects on burnout. When combined, changes in mindfulness and compassion measures correlated with changes in clinical measures at post-treatment and at follow-up. However, heterogeneity was high, probably due to differences in the study design, the implemented protocol, and the assessed outcomes. CONCLUSIONS MBSR is moderately effective in reducing stress, depression, anxiety and distress and in ameliorating the quality of life of healthy individuals; however, more research is warranted to identify the most effective elements of MBSR.