Abstract
QUESTION: Mindfulness-based programmes (MBPs) and practices have demonstrated effects in mental health and well-being, yet questions regarding the target mechanisms that drive change across the population remain unresolved. STUDY SELECTION AND ANALYSIS: Five databases were searched for randomised controlled trials that evaluate the indirect effects (IEs) of an MBP or mindfulness practice in relation to mental health and well-being outcomes through psychological mechanisms. FINDINGS: 27 eligible studies were identified, with only four exploring mechanisms in the context of specific mindfulness practices. Significant IEs were reported for mindfulness skills, decentering and attitudes of mindfulness (eg, self-compassion) across different outcomes, population samples, mental health strategies and active comparators. Evidence gap maps and requirements for testing and reporting IEs are provided to help guide future work. CONCLUSIONS: Mindfulness skills, decentering and attitudes of mindfulness may be key intervention targets for addressing the mental health of whole populations. However, future work needs to address significant knowledge gaps regarding the evidence for alternative mechanisms (eg, attention and awareness) in relation to unique outcomes (eg, well-being), mental health strategies (ie, promotion) and active comparators. High-quality trials, with powered multivariate mediation analyses that meet key requirements, will be needed to advance this area of work. TRIAL REGISTRATION NUMBER: 10.17605/OSF.IO/NY2AH.