McNally, Richard JBaker, Christina WWang, Qiaoqian2026-04-2720262026-04-152026Wang, Qiaoqian. 2026. Symptom Multiplicity: A Phenomenon Contributing to Non-Response Among OCD Patients Receiving Exposure and Response Prevention Therapy. Masters Thesis, Harvard University Division of Continuing Education.32583239https://dash.harvard.edu/handle/1/42735585Exposure and response prevention (ERP) is an effective treatment for obsessive-compulsive disorder (OCD), yet a substantial proportion of patients undergoing ERP fail to achieve clinically meaningful improvement. One underexamined contributor to ERP non-response is “symptom multiplicity,” defined as having multiple elevated OCD symptom dimensions within an individual. The present study investigated whether symptom multiplicity predicts ERP non-response and whether it is associated with distinct processes of change during treatment. Self-reported data were collected from 462 adults with an OCD diagnosis who received ERP from a residential/partial program. Results showed that symptom multiplicity emerged as a significant predictor of ERP non-response after controlling for baseline severity and change in dimensional symptoms and dysfunctional beliefs, indicating that equivalent dimensional improvements translated less consistently into global improvement for this group. Partial correlation networks revealed that global improvement among patients with symptom multiplicity was associated with concurrent changes across multiple dimensions. In contrast, change in dysfunctional belief played a less central role in symptom multiplicity, suggesting limited generalization from fear extinction learning to broader belief changes. Cross-lagged panel networks indicated weak cross-lagged influences between symptoms and beliefs among patients with symptom multiplicity, suggesting no single, optimal sequencing of treating co-occurring dimensional symptoms. Clinical implications, future directions, and limitations were also discussed.application/pdfendysfunctional beliefsexposure and response preventionnetwork analysisobsessive-compulsive disordertreatment mechanismPsychologyThesis or Dissertation2026-04-270009-0007-9412-6139