Efficacy of cognitive behaviour therapy in generalized anxiety disorders - Results of a controlled clinical trial (Berlin CBT-GAD study)

Background: Generalized anxiety disorders ( GAD) are amongst the most prevalent mental disorders. Recent studies have suggested that cognitive behaviour therapy (CBT) is an effective treatment for GAD. A controlled clinical trial was done to evaluate the efficacy of CBT treatment in outpatients with pure GAD who were treated by a therapist working in routine care. Methods: Seventy-two outpatients, fulfilling GAD criteria according to DSM-IV, were included in the study. From this group, 36 patients (CBT-A) were randomly assigned to 25 sessions of CBT and the other 36 formed a contact control group (CCG). After the contact control period ( CC period), these patients were also treated with CBT (CBT-B), allowing not only a parallel group comparison but also an A-B comparison. Therapists were licensed full-time psychologists who worked routinely in outpatient care and had a professional training in CBT. Treatment was done in accordance with a manual, and treatment conformity was controlled by several methods. Results: The reduction in the score on the Hamilton Anxiety Observer Rating Scale was 6.4% (1.5 points) in the CCG, 35.4% (9.5 points) in the CBT-A and 47.3% (10.3 points) in the CBT-B. In the self-rating Spielberger State-Trait Anxiety Inventory, a reduction of 2.7% was seen in CCG, 14.6% in CBT-A, and 11.6% in CBT-B. According to the Clinical Global Impression Rating, 65.6% of patients were still at least moderately ill at the end of the CC period, while this rate was 33.4% at the end of CBT-A, or 15.7% at the end of CBT-B. All these differences between treatment and control group are statistically highly significant. The clinical improvement remained stable over a follow-up period of 8 months. Conclusions: CBT is an effective method of treatment for GAD. Differences between control and treatment group are comparable to or larger than those reported in studies on antidepressant drugs. Copyright (C) 2005 S. Karger AG, Basel.