MBT is an increasingly popular form of therapy for anxiety and mood problems. Two earlier reviews on the effects of MBT on symptoms of anxiety and depression came to contradictory conclusions with regards to the efficacy of these interventions (Baer, 2003; Toneatto & Nguyen, 2007). Since the publication of these reviews, a sufficient number of clinical trials have been published that justifies a comprehensive effect size analysis of this promising treatment.