Assessing the Impact of Metacognitive Therapy on OCD Severity and Beliefs: A Three-Wave Multisite RCT With Panel Mediation Analysis.

Obsessive-compulsive disorder (OCD) is a chronic and disabling condition, and although exposure and response prevention (ERP) is the first-line psychological treatment, many patients decline it, drop out, or retain residual symptoms. According to Wells' metacognitive model, OCD is maintained less by intrusive thoughts themselves than by metacognitive beliefs about the significance, danger, and control of thoughts, which metacognitive therapy (MCT) targets directly. However, individual MCT has been evaluated almost exclusively in high-income Western settings, and whether metacognitive belief change temporally precedes symptom improvement remains untested. This multisite, assessor-blinded randomized controlled trial (RCT) addressed both gaps in Pakistani outpatient services. Seventy-six adults with OCD were randomized to 12 weekly sessions of individual MCT (n = 38) or documented treatment as usual (TAU; n = 38) and assessed at baseline, post-treatment, and 6-month follow-up; outcomes were analyzed with intention-to-treat (ITT) mixed-effects models and an exploratory three-wave panel mediation model. MCT produced greater reductions in clinician-rated Yale-Brown Obsessive-Compulsive Scale severity than TAU, F(1.81, 134) = 11.30, p < 0.001, with mean differences of -4.00 at post-treatment and -6.92 at follow-up (both p < 0.001) and more frequent treatment response. MCT also reduced Metacognitions Questionnaire-30 belief domains, with gains maintained at follow-up. However, the prespecified lagged indirect effect through post-treatment beliefs was not supported (β = -0.01). Findings extend the evidence for MCT to a non-Western clinical context and suggest that broad metacognitive belief domains behave as markers of clinical state rather than proximal mechanisms, underscoring the need for temporally fine-grained mechanism research.