Efficacy of Exposure and Response Prevention(ERP) and SSRIs in Chinese OCD Patients

Inclusion Criteria: * Having been diagnosed with primary OCD as defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-) criteria;Cleaning or checking as primary OCD symptoms * Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) score of ≥ 16 * Never receiving adequate treatment or stop receiving treatment for at least 8 weeks * Having an education degree of high school or above * Accepting to participate in the study Exclusion Criteria: * Having significant medical illnesses that would interfere with the conduct of the study * Clinically significant abnormal laboratory finding * Having comorbid psychiatric conditions according to the criteria set forth in the DSM-IV(administered by the Mini-International Neuropsychiatric Interview (MINI)) * The current OCD symptoms are too severe that the patient cannot finish the evaluation or receive the ERP * Being currently at risk for suicide * Being pregnant or having the intention to be pregnant before the end of the study * A history of having inadequate response to adequate SSRIs or CBT treatment * Subjects who are unable to undergo the MRI