Concentrated Exposure Therapy vs Internet-Based Cognitive Behavioral Therapy for Obsessive-Compulsive Disorder: A...

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.

To evaluate the efficacy of B4DT compared with internet-based cognitive behavioral therapy (iCBT) in reducing OCD symptom severity.

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.

Patients were randomized to B4DT (including preparatory sessions) or an 8-week unguided iCBT program.

The primary outcome was the change in OCD symptom severity, measured by the Yale-Brown Obsessive Compulsive Scale (Y-BOCS). Secondary outcomes included self-reported OCD (OCI-R), dysfunctional cognitions, quality of life, depressive symptoms, experiential avoidance, global functioning, self-esteem, and treatment satisfaction.

A total of 253 individuals were screened, and 119 were enrolled after 53 were found to be ineligible and 81 declined to participate. Sixty of the 119 randomized participants (mean [SD] age, 33.5 [10.1] years; 79 [66.4%] women) were assigned to B4DT and 59 to iCBT. The primary analysis included all randomized participants (intention-to-treat). B4DT was associated with significantly greater reductions in OCD symptoms (Y-BOCS) than iCBT, with large effects at posttreatment (mean [SE] difference, -7.9 [0.9]; 95% CI, -9.7 to -6.0; Hedges g, -1.6) and sustained effects at 3-month follow-up (mean [SE] difference, -5.6 [1.1]; 95% CI, -7.8 to -3.4; Hedges g, -1.0). Secondary outcomes consistently favored B4DT. Response and remission rates at 3-month follow-up were higher with B4DT (35 of 57 [61.4%] vs 11 of 44 [25.0%] and 24 of 57 [42.1%] vs 6 of 44 [13.6%], respectively).

In this randomized clinical trial of 119 adults with OCD, B4DT was superior to iCBT in reducing OCD symptom severity, with sustained benefits. Its brief, concentrated format may represent a scalable strategy to improve access to effective OCD treatment globally.

German Clinical Trials Register: DRKS00034236.