In general, the observed effect sizes were unrelated to publication year, treatment length, or study quality. Finally, the follow-up data suggested that the effects were maintained at follow-up (with a median follow-up period of 12 weeks). It should be noted that conventional CBT (i.e., without mindfulness procedures) is also quite effective for depression and anxiety disorders (e.g., Butler, Chapman, Forman, & Beck, 2006; Hofmann & Smits, 2008a). In their review of meta-analyses examining the efficacy of conventional CBT for unipolar depression, generalized anxiety disorder, panic disorder with or without agoraphobia, social anxiety disorder, and PTSD, Butler et al. (2006) estimated the effect size to be 0.95 (SD: 0.08). Future studies should directly compare the efficacy, cost-effectiveness, patient (and therapist) preference, treatment acceptability, and attrition of conventional CBT and MBT.
