Background: Cognitive behaviour therapy (CBT) is an effective treatment for obsessive-compulsive disorder (OCD) but access to CBT is limited. Internet-based CBT (ICBT) with therapist support is potentially a more accessible treatment. There are no randomized controlled trials testing ICBT for OCD. The aim of this study was to investigate the efficacy of ICBT for OCD in a randomized controlled trial.
Method: Participants (n=101) diagnosed with OCD were randomized to either 10 weeks of ICBT or to an attention control condition, consisting of online supportive therapy. The primary outcome measure was the Yale-Brown Obsessive Compulsive Scale (YBOCS) administered by blinded assessors.
Results: Both treatments lead to significant improvements in OCD symptoms, but ICBT resulted in larger improvements than the control condition on the YBOCS, with a significant between-group effect size (Cohen's d) of 1.12 (95% CI 0.69-1.53) at post-treatment. The proportion of participants showing clinically significant improvement was 60% (95% CI 46-72) in the ICBT group compared to 6% (95% CI 1-17) in the control condition. The results were sustained at follow-up.
Conclusions: ICBT is an efficacious treatment for OCD that could substantially increase access to CBT for OCD patients. Replication studies are warranted.