Effectiveness of Acceptance and Commitment Therapy on Obsessive Beliefs Among Patients With Obsessive-Compulsive Disorder.

OBJECTIVE: Both acceptance and commitment therapy (ACT) and metacognitive therapy (MCT) for obsessive-compulsive disorder (OCD) target metacognition. In this context, ACT's therapeutic effects on OCD are presumably reflected in the Obsessive Belief Questionnaire (OBQ), which incorporates significant metacognitive factors. However, most studies have investigated ACT's effects on OCD symptoms rather than on obsessive beliefs. METHODS: This study examined the relationship between ACT process measures-Acceptance and Action Questionnaire-II (AAQ-II) and Cognitive Fusion Questionnaire (CFQ)-and the OBQ following an 8-week group-format ACT (GACT) intervention among patients with OCD (GACT group, n=37; wait-list control group, n=42). RESULTS: Significant reductions were observed in AAQ-II, CFQ, and OBQ scores after treatment. Changes in AAQ-II and CFQ (particularly in the former) were significantly associated with changes in the OBQ total and subscale scores. These measures accounted for 26% and 12% of the variance in the OBQ total score and OCD symptom scores, respectively. Among OBQ subscales, changes in AAQ-II and CFQ best accounted for the variance of perfectionism and intolerance of uncertainty (OBQ-PU), followed by importance and control of thoughts (OBQ-ICT). CONCLUSION: Improvements in ACT process measures through GACT were more strongly linked to obsessive beliefs than to OCD symptoms, highlighting the role of obsessive beliefs-particularly OBQ-PU and OBQ-ICT-in ACT's effectiveness for OCD.