Correcting and interpreting the effect of cognitive therapy versus exposure in anxiety disorders

We read with great interest the systematic review evaluating the efficacy of exposure versus cognitive therapy (CT) in anxiety disorders, performed by Dr. Dennis Ougrin [1]. The author meta-analysed 20 randomised controlled trials (RCTs) comparing CT versus exposure in four anxiety disorders and concluded the following: “there appears to be no evidence of differential efficacy between cognitive therapy and exposure in PD [panic disorder], PTSD [posttraumatic stress disorder] and OCD [obsessive compulsive disorder] and strong evidence of superior efficacy of cognitive therapy in social phobia” [1].Upon reviewing the short-term and long-term results of CT versus exposure in patients with Social Phobia, we found two errors. First, the summary effect (standard error [SE]) for the short-term outcome in Hofmann (2004) was incorrectly inputted as ？0.28 (0.26). We contacted Dr. Stefan Hofmann [2], obtained the raw data from the published trial, and found that the correct summary effect (SE) was ？0.19 (0.27). Second, Dr. Ougrin states, “the overall effect (the end-of-treatment standardised mean difference (SMD), Hedge’s g) is summarised in Figure 7” [1]. The forest plot, however, does not indicate what summary effect was reported in the pooled analysis and thus the assumption was made that it was the SMD. Upon replicating the meta-analysis, we found that the summary effect was incorrectly pooled as an odds ratio (OR), i.e. OR (95% confidence interval [CI]) of 0.52 (0.37, 0.74) for short-term outcomes. Thus, we inputted the correct summary effect for Hofmann 2004 and re-analysed the meta-analysis using SMD for our summary effect, as originally intended. We found that the corrected SMD (95% CI) was ？0.66 (？1.19, -0.14) for short-term outcomes. We used the random effects model given that the i2 was 56% (Figure 1). Using the Cohen’s d criteria of 0.2 to represent a small effect, 0.5 a medium effect and 0.8 a large effect [3], we found that CT has a medium effect in improving soc