Mental wellbeing predicts mental and physical health outcomes, and has been hailed as one of the ultimate aims in public health in recent years10. Universal interventions to promote mental wellbeing and prevent mental health problems are thought to be effective because more people from low risk groups will ultimately develop a problem than those at risk. Combining preventative mental health interventions with stratified medicine approaches could lead to advantages in effectiveness, cost-effectiveness, and intervention harm minimisation11.Mindfulness-based interventions (MBIs) to promote mental health have become extremely popular. Major UK organisations have introduced them, including 30 universities and several NHS trusts, civil service departments and private employers12 13. However, an overview of systematic reviews conducted for this application revealed that the evidence for preventative MBIs is weak, consisting of scattered small randomised controlled trials (RCTs) suggesting positive effects but high inter-individual variability. Many uncertainties remain: most RCTs have high risk of type I and II errors; there are publication bias concerns; effects of different types of MBIs are obscure; results against active controls are mixed; and there is evidence that not everyone benefits from mindfulness training. High-quality systematic reviews and meta-analyses on the topic are lacking. In 2015 an All-Party Parliamentary Group recommended that the NIHR funds research on mindfulness as a public health preventative intervention13.An individual participant data (IPD) meta-analysis of preventative MBIs would cost-effectively improve the quality of inferred results based on existing data overcoming some of the existing biases, and would provide the largest possible sample size to explore how MBI effectiveness varies as function of individual and study differences14.
The primary aims of this study are to: (a) evaluate the effectiveness of MBIs for reducing distress, anxiety and depression, and improving mental wellbeing, self-care and performance among community adults, compared with no intervention or a comparator intervention; and (b) assess predictors of differential intervention response at individual (e.g. baseline mental distress) and study (e.g. length of intervention) levels.
Plan of investigation:
To address the research aims, an IPD meta-analysis will be conducted. Published and unpublished RCTs, assessing MBIs of at least four sessions, among adult participants living in the community not selected for having any particular illness or disability will be systematically reviewed following a prospectively registered protocol with pre-defined outcomes. RCTs' risk of bias will be assessed, and aggregate data meta-analyses will be conducted.Authors of trials with 90 or more participants will be invited to contribute IPD15. Sixteen studies from the overview (N=2,886) are eligible. Thanks to preliminary agreements with nine of them, 61% of the eligible trials' participants (N=1,765) are readily available. Data will be checked, queried, standardised, and re-analysed for each RCT following the intention-to-treat principle. IPD random-effects meta-analyses will be performed comparing MBIs against active (non-specific and other interventions) and passive control groups. Heterogeneity, publication bias and sensitivity analyses will be carried out. Predetermined predictors differential response to the intervention will be assessed and prognostic modelling will be attempted16.Steering and Stakeholder groups including members of the public will provide input throughout the life of the project, from protocol decisions to interpretation and dissemination of results, following a co-production model5.
Benefit for the public:
Outputs will significantly benefit the public within five years of project completion by determining the effectiveness of preventative MBIs and improving their targeting in a variety of settings, consequently improving communities' mental health and wellbeing, and generating a more efficient use of public resources. Impact will also be achieved by increasing public awareness and understanding of preventative research and by promoting the adoption of evidence-based stress management techniques.