The Impact of Group-Based Mindfulness Training on Self-Reported Mindfulness: a Systematic Review and Meta-analysis

Mindfulness-based interventions (MBIs) show promising results in both clinical and non-clinical settings. A number of studies indicate that self-reported mindfulness is associated with adaptive psychological functioning and decreased symptom distress. However, there have been no systematic reviews of research on self-reported mindfulness as an outcome of MBIs for clinical and non-clinical samples. It is also unclear to what extent MBIs actually lead to increased and stable self-reported mindfulness. A systematic literature search was conducted to identify studies measuring self-reported mindfulness before and after an MBI. Meta-analytic procedures were used to investigate self-reported mindfulness as an outcome of MBIs. The results show that several questionnaires have been designed to measure mindfulness, and these have been applied to a variety of samples. Although methodological issues preclude definite conclusions, the meta-analysis indicates that MBIs increase self-reported mindfulness. Effect sizes indicate that increases are in the medium range (Hedges’ g = 0.53). However, over half of the studies found no significant effects of MBIs on self-reported mindfulness from pre- to post-intervention. Also, studies of MBIs against active control conditions show no significant advantage for MBIs in increasing self-reported mindfulness. This raises serious questions concerning the validity of the mindfulness questionnaires currently in use. The addition of...