Mindfulness-based programmes for mental health promotion in adults in nonclinical settings: A systematic review and meta-analysis of randomised controlled trials

Author summary Why was this study done? Mindfulness courses to increase well-being and reduce stress have become very popular; most are in community settings. Many randomised controlled trials (RCTs) tested whether mindfulness courses show benefit, but results are varied and, to our knowledge, there are no reviews combining the data from these studies to show an overall effect. What did the researchers do and find? Worldwide, we identified 136 RCTs on mindfulness training for mental health promotion in community settings. We reviewed them all, assessed their quality, and calculated their combined effects. We showed that, compared with doing nothing, mindfulness reduces anxiety, depression, and stress, and increases well-being, but we cannot be sure that this will happen in every community setting. In these RCTs, mindfulness is neither better nor worse than other feel-good practices such as physical exercise, and RCTs in this field tend to be of poor quality, so we cannot be sure that our combined results represent the true effects. What do these findings mean? Mindfulness courses in the community need to be implemented with care, because we cannot assume that they work for everyone, everywhere. We need good quality collaborative research to find out which types of communities benefit from the different types of mindfulness courses available. The courses that work best may be those aimed at people who are most stressed or in stressful situations. Background There is an urgent need for mental health promotion in nonclinical settings. Mindfulness-based programmes (MBPs) are being widely implemented to reduce stress, but a comprehensive evidence synthesis is lacking. We reviewed trials to assess whether MBPs promote mental health relative to no intervention or comparator interventions. Methods and findings Following a detailed preregistered protocol (PROSPERO CRD42018105213) developed with public and professional stakeholders, 13 databases were searched to August 2020 for randomised controlled trials (RCTs) examining in-person, expert-defined MBPs in nonclinical settings. Two researchers independently selected, extracted, and appraised trials using the Cochrane Risk-of-Bias Tool 2.0. Primary outcomes were psychometrically validated anxiety, depression, psychological distress, and mental well-being questionnaires at 1 to 6 months after programme completion. Multiple testing was performed using p < 0.0125 (Bonferroni) for statistical significance. Secondary outc