Correcting and interpreting the effect of cognitive therapy versus exposure in anxiety disorders.
Bottom Line: These were incorrectly meta-analysed.For PTSD, the SMD (95% CI) for short-term outcomes was -0.13 (-0.36, 0.11) and 0.05 (-0.22, 0.32) for long-term outcomes.However, correcting the errors did not change the interpretation of the findings considerably.
Dr. Ougrin's evaluation of cognitive therapy versus exposure in anxiety disorders reported a standardised mean difference [SMD] (95% confidence interval [CI]) of 0.52 (0.37, 0.74) for short-term outcomes and 0.46 (0.29, 0.73) for long-term outcomes in social phobia, and 0.88 (0.69, 1.11) for short-term outcomes and 1.05 (0.80, 1.37) for long-term outcomes in posttraumatic stress disorder (PTSD). These were incorrectly meta-analysed. Upon re-analysis, we found that the correct SMD (95% CI) was -0.66 (-1.19, -0.14) for short-term outcomes and mean difference (95% CI) of -29.66 (-46.13, -13.19) on the Social Phobia subscale from the Social Phobia Anxiety Inventory for long-term outcomes in Social Phobia. For PTSD, the SMD (95% CI) for short-term outcomes was -0.13 (-0.36, 0.11) and 0.05 (-0.22, 0.32) for long-term outcomes. However, correcting the errors did not change the interpretation of the findings considerably.
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Mentions: 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, 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”. 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% (Figure1). 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, we found that CT has a medium effect in improving social phobia versus exposure with the lower bounds of the 95% CI in the range of a modest effect, for short-term outcomes.