Multiple meta analyses and reviews over the past 30 years have concluded that CBT is an effective treatment across a range of substance use disorders (Carroll & Onken, 2005; Dutra et al., 2008; Irvin, Bowers, Dunn, & Wong, 1999; Magill & Ray, 2009). The most recent and comprehensive meta-analysis included 53 controlled trials, published through 2006, of CBT for adults diagnosed with alcohol or drug use disorders, and reported a small but statistically significant treatment effect (g = 0.15) for CBT over control conditions across studies (Magill & Ray, 2009). Statistical transformations to a ‘success percentage’ indicated 58% of patients receiving CBT fared better than those in the comparison condition (Magill & Ray, 2009). Effect size varied according to the type of comparison condition, with a large effect size found for CBT in comparison to no treatment (random g = .80, p < .005), and small-sized effects in comparison to a passive (random g = .15, p < .005) or active treatment (random g = .13, p < .05). Also, larger effect sizes were found in studies of CBT combined
