Randomized controlled trial on the effectiveness of metacognitive therapy and intolerance-of-uncertainty therapy for generalized anxiety disorder.

This randomized controlled trial compared the effectiveness of metacognitive therapy (MCT) and intolerance-of-uncertainty therapy (IUT) for generalized anxiety disorder (GAD) in an outpatient context. Patients with GAD (N = 126) consecutively referred to an outpatient treatment center for anxiety disorder were randomly allocated to MCT, IUT, or a delayed treatment (DT) condition. Patients were treated individually for up to 14 sessions. Assessments were conducted before treatment (pretreatment), after the last treatment session (posttreatment), and six months after treatment had ended (follow-up). At posttreatment and follow-up assessments, substantial improvements were observed in both treatment conditions across all outcome variables. Both MCT and IUT, but not DT, produced significant reductions in GAD-specific symptoms with large effect sizes (ranging between 0.94 and 2.39) and high proportions of clinically significant change (ranging between 77% and 95%) on various outcome measures, and the vast majority of the patients (i.e., 91% in the MCT group, and 80% in the IUT group) no longer fulfilled the diagnostic criteria for GAD. Results further indicate that MCT produced better results than IUT. This was evident on most outcome measures, and also reflected in effect sizes and degree of clinical response and recovery.