Importance: Cognitive behavior therapy (CBT) is a first-line treatment for most mental disorders. However, no meta-analytic study has yet integrated the results of randomized clinical trials on CBT across different disorders, using uniform methodologies and providing a complete overview of the field.

Objective: To examine the effect sizes of CBT for 4 anxiety disorders, 2 eating disorders, major depression, obsessive-compulsive disorder (OCD), posttraumatic stress disorder (PTSD), and psychotic and bipolar disorders on symptoms of the respective disorders using uniform methodologies for data extraction, risk of bias (RoB) assessment, and meta-analytic techniques.

Data sources: Major bibliographical databases (PubMed, PsycINFO, and Embase for all disorders) were searched up to January 1, 2024, for each disorder separately. Data analysis was performed from August 2024 to January 2025.

Study selection: Randomized clinical trials comparing CBT with inactive control conditions in adults with 1 of the mental disorders established through a clinical interview were included.

Data extraction and synthesis: Basic characteristics of patients, CBT, and studies were extracted. RoB was assessed with the Cochrane RoB tool 2. Meta-analyses were conducted using random-effects models.

Main outcomes and measures: The primary outcome was the standardized mean difference (Hedges g) indicating the difference between CBT and controls at posttreatment on symptoms of the respective disorders.

Results: A total of 375 trials (423 comparisons) between CBT and controls were included among 32 968 patients. The overall mean (SD) patient age was 43.4 (13.7) years, and the mean (SD) proportion of women was 0.68 (0.24). Effect sizes for CBT compared to all control conditions (g) were lower than 0.5 for bipolar and psychotic disorder; between 0.5 and 1.0 for panic, social anxiety, and generalized anxiety disorders, bulimia nervosa, binge eating disorders, depression, and OCD; and larger than 1.0 for PTSD and specific phobias (range of effect sizes: 0.31 for bipolar disorder to 1.27 for PTSD). Large effect sizes (g > 0.94) were observed in waitlist-controlled trials, a control condition mostly used in anxiety and eating disorders, PTSD, and OCD. Trials using care as usual showed more modest effect sizes (0.22-1.13). Study dropout rates within the CBT conditions ranged from 8% for specific phobia to 24% for PTSD.

Conclusions and relevance: In this unified series of meta-analyses, CBT was probably effective in the treatment of mental disorders, including major depression, anxiety disorders, PTSD, OCD, and eating disorders, and possibly effective in psychotic and bipolar disorders. However, the effect sizes depended on the type of control condition.

Author/s:

Pim Cuijpers, Mathias Harrer, Clara Miguel, Marketa Ciharova, Davide Papola, Djordje Basic, Cristina Botella