Transdiagnostic metacognitive therapy compared to disorder-specific cognitive behavioral therapy for anxiety disorders: a study protocol for a randomized controlled superiority trial

Background Anxiety disorders are highly prevalent worldwide and are associated with functional impairment, reduced quality of life and high societal costs. With only approximately 50% of patients achieving remission following cognitive behavioral therapy (CBT), the evaluation of other effective treatments is warranted. Studies suggest that metacognitive therapy (MCT) may be more effective than CBT for anxiety disorders. Although transdiagnostic treatment may be beneficial for treatment implementation and dissemination in routine care, there is currently only one adequately powered study comparing transdiagnostic MCT (tMCT) to disorder-specific CBT for anxiety disorders. The main aim of this trial is to investigate the effectiveness of tMCT compared to disorder-specific CBT for anxiety disorders. The trial also aims to investigate potential mediators of treatment effects in tMCT and CBT, to conduct a health economic evaluation and to explore patients' perspectives on the treatments. Methods This trial is a prospective, pragmatic, two-arm parallel-group randomized controlled superiority trial comparing tMCT with disorder-specific CBT, conducted in outpatient psychiatric services in Stockholm, Sweden. A sample of 86 adults with a principal diagnosis of generalized anxiety disorder, social anxiety disorder or posttraumatic stress disorder will be recruited and randomly allocated to tMCT or CBT. Primary outcomes are self-rated symptoms of principal diagnosis, and secondary outcomes are clinical severity, remission rates, depressive symptoms, functional impairment and quality of life. Outcomes will be assessed at pre- and post-treatment as well as at 6- and 12-month follow-up. Metacognitions and cognitions as potential mediators will be measured weekly during treatment. Cost-effectiveness of tMCT compared to CBT will be investigated. Semi-structured interviews will be conducted with participants from both conditions. Discussion Considering the potential of MCT, further research is needed to evaluate its effectiveness compared to CBT, particularly MCT in a transdiagnostic format. Results from this trial will add to the evidence base for tMCT and inform treatment development, decision-making and implementation of effective treatment for anxiety disorders in routine care. Trial registration ClinicalTrials.gov NCT06937892.