Integrating ACT with ERP for OCD treatment: A randomized controlled trial examining symptom reduction and psychological flexibility mechanisms

Despite Exposure and Response Prevention's (ERP) established efficacy for Obsessive-Compulsive Disorder (OCD), there is growing interest in exploring complementary therapeutic approaches that may enhance treatment outcomes through different mechanisms of change. This study investigated the efficacy of combined Acceptance and Commitment Therapy plus ERP (ACT + ERP) in treating OCD and its underlying psychological mechanisms in an Iranian sample.

A randomized controlled trial was conducted with 40 OCD-diagnosed participants, randomly allocated to ACT + ERP intervention (n = 20) or wait-list control group (n = 20). The intervention comprised sixteen 120-min sessions delivered twice weekly. Assessments were conducted at baseline, post-treatment, and three-month follow-up using the Obsessive-Compulsive Inventory-Revised (OCI-R), Acceptance and Action Questionnaire-II (AAQ-II), Cognitive Fusion Questionnaire (CFQ), and Interpretation of Intrusions Inventory (III-31).

Mixed-model ANOVAs revealed significant time × group interactions across all measures. The ACT + ERP group demonstrated substantial improvements in OCD severity (η² = 0.301), experiential avoidance (η² = 0.139), cognitive fusion (η² = 0.241), and interpretation of intrusions (η² = 0.217). Large effect sizes were maintained at follow-up (Hedges’ g ranging from 0.75 to 1.20). The waitlist group showed no significant changes.

The integrated ACT + ERP protocol effectively reduced OCD symptoms and improved psychological flexibility processes, with benefits maintained at follow-up. These findings suggest that combining ACT and ERP may offer a comprehensive treatment approach that enhances therapeutic outcomes through multiple mechanisms of change.