Abstract

Cognitive behavior therapy (CBT) is by far the most examined type of psychological treatment for depression and is recommended in most treatment guide­lines. However, no recent meta-analysis has integrated the results of randomized trials examining its effects, and its efficacy in comparison with other psychotherapies, pharmacotherapies and combined treatment for depression remains uncertain. We searched PubMed, PsycINFO, Embase and the Cochrane Library to identify studies on CBT, and separated included trials into several subsets to conduct random-effects meta-analyses. We included 409 trials (518 comparisons) with 52,702 patients, thus conducting the largest meta-analysis ever of a specific type of psychotherapy for a mental disorder. The quality of the trials was found to have increased significantly over time (with increasing numbers of trials with low risk of bias, less waitlist control groups, and larger sample sizes). CBT had moderate to large effects compared to control conditions such as care as usual and waitlist (g=0.79; 95% CI: 0.70-0.89), which remained similar in sensitivity analyses and were still significant at 6-12 month follow-up. There was no reduction of the effect size of CBT according to the publication year (<2001 vs. 2001-2010 vs. >2011). CBT was significantly more effective than other psychotherapies, but the difference was small (g=0.06; 95% CI: 0-0.12) and became non-significant in most sensitivity analyses. The effects of CBT did not differ significantly from those of pharmacotherapies at the short term, but were significantly larger at 6-12 month follow-up (g=0.34; 95% CI: 0.09-0.58), although the number of trials was small, and the difference was not significant in all sensitivity analyses. Combined treatment was more effective than pharmacotherapies alone at the short (g=0.51; 95% CI: 0.19-0.84) and long term (g=0.32; 95% CI: 0.09-0.55), but it was not more effective than CBT alone at either time point. CBT was also effective as unguided self-help intervention (g=0.45; 95% CI: 0.31-0.60), in institutional settings (g=0.65; 95% CI: 0.21-1.08), and in children and adolescents (g=0.41; 95% CI: 0.25-0.57). We can conclude that the efficacy of CBT in depression is documented across different formats, ages, target groups, and settings. However, the superiority of CBT over other psychotherapies for depression does not emerge clearly from this meta-analysis. CBT appears to be as effective as pharmacotherapies at the short term, but more effective at the longer term.

DISCUSSION

This is the largest meta-analysis ever of a specific type of psychotherapy for a mental disorder, including 409 RCTs (518 comparisons) with 52,702 patients. CBT was found to be effective in depression when compared to control conditions such as usual care and waitlist, with a moderate to large effect size (g=0.79). This effect was robust in several sensitivity analyses, although it was somewhat smaller for studies with low risk of bias (g=0.60) and after adjustment for publication bias (g=0.47). CBT was still significantly effective at 6-9 month (g=0.74) and 10-12 month (g=0.49) follow-up, and this was confirmed in most sensitivity analyses.

A total of 42% of patients receiving CBT responded to treatment, while the response rate was only 19% in control groups, with a NNT of 4.7 in favor of CBT. The remission rate was 36% in patients receiving CBT, compared to 15% in control conditions, with a NNT of 3.6.

Comparative trials suggest that CBT is significantly more effective than other psychotherapies, but the difference is small (g=0.06) and does not remain significant in most sensitivity analyses. The effects of CBT are comparable to those of pharmacotherapies at the short term, but CBT is significantly more effective at 6 to 12 months (g=0.34). Combined treatment is significantly more effective than pharmacotherapy alone, at the short (g=0.51) and the longer term (g=0.32), but combined treatment is not more effective than CBT alone at either time point.

Most trials examine CBT in an individual, group or guided self-help format, and we previously showed that there are no significant differences between these formats¹². In the current meta-analysis, we could also include a set of trials of unguided self-help CBT, and found that this was also effective, with a small to moderate effect size (g=0.45). CBT was also found to be effective in inpatient settings (g=0.65), as well as in children and adolescents (g=0.41).

Research on CBT has evolved over time. The quality of studies has improved, which can be seen from the increasing number of trials with low risk of bias, the decrease in the use of waitlist control groups, and the increase in sample sizes of included studies. The number of treatment sessions has significantly decreased over the years. In a meta-regression analysis, we could not confirm that the effect size of CBT has decreased over time, as was suggested in an earlier study³⁷.

The findings of this study should be considered in the light of some limitations. First, heterogeneity was high in many analyses, and subgroup and meta-regression analyses could not identify all sources of this heterogeneity, suggesting that there are differences between trials that cannot be explained by the extracted characteristics. Second, risk of bias was high in many of the included trials, and the effect sizes of the trials with low risk of bias were significantly lower in some of the analyses. Fortunately, the number of studies was so large that we could examine outcomes in subsets of trials with low risk of bias. Finally, we found indications of publication bias in many analyses, although several findings remained robust after correcting for this bias.

We can conclude that CBT is effective in the treatment of depression with a moderate to large effect size, and that its effect is still significant up to 12 months. The superiority of CBT over other psychotherapies does not emerge clearly from this meta-analysis. CBT appears to be as effective as pharmacotherapies at the short term, but more effective at the longer term. Combined treatment appears to be superior to pharmacotherapy alone but not to CBT alone. The efficacy of CBT in depression is documented across different delivery formats, ages, target groups, and settings.

Source: onlinelibrary.wiley.com