Baseline trait mindfulness moderates the efficacy of mindfulness interventions and active controls: A meta-analysis of 177 randomised controlled trials.

Previous evidence suggests that benefits of mindfulness-based interventions (MBIs) may depend on individuals' baseline trait mindfulness (BTM) levels. This meta-analysis investigated moderating effects of BTM on changes in mental health outcomes and trait mindfulness in randomised controlled trials (RCTs) of MBIs. A total of 177 primary studies (total N = 13,486), comparing the treatment effects of MBIs against active, treatment-as-usual (TAU) and waitlist control groups, were synthesised via three-level meta-analysis. Lower BTM was associated with larger changes in mental health outcomes (B = -0.14, 95% CI [-0.21, -0.06], p < .001) and trait mindfulness (B = -0.09 [-0.16, -0.02], p = .009) in MBIs and active controls combined. These associations were significantly larger than from those in TAU and waitlist controls. Moderating effects were less tangible for changes in trait mindfulness in MBIs and active controls individually and less tangible in various sensitivity analyses which, however, were confounded by client type across the RCTs. Individuals low in BTM may, by a small effect size, benefit more from MBIs and active control interventions. BTM may thus affect the evaluation of treatment efficacy. MBIs and active interventions could be offered specifically to persons low in BTM.