Clinical and Neuroimaging Effects of Mindfulness-Based Cognitive Therapy for Symptomatic Obsessive-Compulsive Disorder Patients after First-Line Treatments: A Randomised Controlled Trial

Introduction: Obsessive-compulsive disorder (OCD) is a chronic condition where many patients remain symptomatic despite first-line treatments such as cognitive behavioural therapy and selective serotonin reuptake inhibitors. This randomised controlled trial evaluated mindfulness-based cognitive therapy (MBCT) efficacy as an augmentation strategy and its impact on brain functional connectivity. Methods: Sixty-eight participants with moderately symptomatic OCD were randomised into MBCT or treatment as usual (TAU). Clinical outcomes were evaluated using the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) and the Obsessive-Compulsive Inventory, alongside other relevant secondary outcomes. Data were analysed using repeated-measures ANOVA to assess time * group effects. Neuroimaging functional measures (resting-state network connectivity) were collected before and after the intervention and analysed using independent component analysis. Results: Primary outcome: MBCT significantly reduced OCD symptoms compared to TAU (31.73% vs. 8.07% Y-BOCS reduction). Secondary outcomes: the MBCT group also experienced reductions in depressive symptoms, rumination, perceived stress, and quality of life. No significant post-treatment changes were observed in resting-state connectivity. However, baseline connectivity demonstrated significant predictive value, with lower connectivity in preselected networks of interest, including the fronto-striatal, salience, and default mode networks, associated with greater reductions in Y-BOCS scores. Conclusion: MBCT is an effective strategy for individuals with moderately symptomatic OCD who continue to experience symptoms despite prior gold-standard treatments. While no post-treatment changes in brain functional connectivity were observed, baseline connectivity patterns predicted symptom reduction, suggesting a neural basis for MBCT response.