Background: There is a need to regularly update the evidence base on the effectiveness of online mindfulness-based interventions (MBIs), especially considering how fast this field is growing and developing. Objective: This study presents an updated meta-analysis of randomized controlled trials assessing the effects of online MBIs on mental health and the potential moderators of these effects. Methods: We conducted a systematic literature search in PsycINFO, PubMed, and Web of Science up to December 4, 2020, and included 97 trials, totaling 125 comparisons. Pre-to-post and pre-to-follow-up between-group effect sizes (Hedges g) were calculated for depression, anxiety, stress, well-being, and mindfulness using a random effects model. Results: The findings revealed statistically significant moderate pre-to-post effects on depression (g=0.34, 95% CI 0.18-0.50; P<.001), stress (g=0.44, 95% CI 0.32-0.55; P<.001), and mindfulness (g=0.40, 95% CI 0.30-0.50; P<.001) and small effects on anxiety (g=0.26, 95% CI 0.18-0.33; P<.001). For well-being, a significant small effect was found only when omitting outliers (g=0.22, 95% CI 0.15-0.29; P<.001) or low-quality studies (g=0.26, 95% CI 0.12-0.41; P<.001). Significant but small follow-up effects were found for depression (g=0.25, 95% CI 0.12-0.38) and anxiety (g=0.23, 95% CI 0.13-0.32). Subgroup analyses revealed that online MBIs resulted in higher effect sizes for stress when offered with guidance. In terms of stress and mindfulness, studies that used inactive control conditions yielded larger effects. For anxiety, populations with psychological symptoms had higher effect sizes. Adherence rates for the interventions ranged from 35% to 92%, but most studies lacked clear definitions or cut-offs. Conclusions: Our findings not only demonstrate that online MBIs are booming but also corroborate previous findings that online MBIs are beneficial for improving mental health outcomes in a broad range of populations. To advance the field of online MBIs, future trials should pay specific attention to methodological quality, adherence, and long-term follow-up measurements.
- Mental health
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