The aim of this presentation is to report the efficacy of MPPIs, through a systematic review and meta-analysis. We included 50 randomized controlled trials
that were published in 51 articles between 1998 and August 2018. We found standardized mean differences of Hedges’ g = 0.34 for subjective well-being, Hedges’ g = 0.39 for
psychological well-being, indicating small to moderate effects, and Hedges’ g = 0.29 for depression, and Hedges’ g = 0.35 for anxiety and stress, indicating small effects. Removing
outliers led to a considerable decrease in effect sizes for subjective well-being and depression, a slight decrease for psychological well-being, and a strong increase in the effect size
for stress. Moderator analyses only showed a significant effect for study quality, showing larger effect sizes for low quality studies compared to
studies of moderate and high quality. In addition, a larger effect size for anxiety was found in studies from non-Western countries compared to studies from Western countries. In
sum, this systematic review and meta-analysis found evidence for the efficacy of MPPIs in improving mental health.