Concentrated Exposure Therapy vs Internet-Based Cognitive Behavioral Therapy for Obsessive-Compulsive Disorder: A Randomized Clinical Trial

Importance: Given the high prevalence, chronicity, and associated disability of obsessive-compulsive disorder (OCD), optimizing treatment is a global priority. The Bergen 4-day treatment (B4DT), a concentrated exposure-based intervention, may reduce treatment burden and improve access to evidence-based care.

Objective

To evaluate the efficacy of B4DT compared with internet-based cognitive behavioral therapy (iCBT) in reducing OCD symptom severity. Design, setting, and participants: Single-center randomized controlled trial (1:1 allocation). Between May 8, 2024, and August 8, 2025, adults (aged 18 to 72 years) with OCD were enrolled and were followed up for 3 months. Key exclusion criteria included schizophrenia, bipolar disorder, acute suicidality, substance dependence, and recent psychopharmacological changes. Outcomes were assessed at baseline, 6 weeks, 8 weeks (posttreatment), and 3 months (follow-up) by masked evaluators.