The purpose of this study is to assess the efficacy of Escitalopram in the treatment of obsessive compulsive disorder and to determine the optimal treatment dose.

Background and Purpose: Obsessive compulsive disorder affects approximately 3% of the population. Treatment options include the selective serotonin reuptake inhibitors (SSRIs), dual serotonin and norepinephrine reuptake inhibitors, and behavioral therapy. A recent double-blind, placebo-controlled trial demonstrated that citalopram is effective in the treatment of OCD. Escitalopram is a new SSRI that may be more effective than other SSRIs for the treatment of major depression and may have fewer side effects. This study aims to assess the efficacy of escitalopram for the treatment of OCD.

Comparisons: Subject Y-BOCs pre-post treatment. We will also compare the improvement of subjects across the three different medication levels: 10 mg, 20 mg, and 30 mg.

Inclusion Criteria:

• Diagnosis of OCD by DSM-IV
• Age 18-65
• Y-BOCS greater than 20
• Written informed consent
• Females of childbearing potential must have a negative serum or urinary beta-HCG test.

Exclusion Criteria:

• Pregnant women or women of childbearing potential who are not using a medically accepted means of contraception.
• Patients who, in the investigator's judgement, pose a serious suicidal or homicidal risk.
• Serious or unstable medical illness including cardiovascular, hepatic, renal, respiratory, endocrine, neurologic, or hematologic disease. Patients on anticoagulant therapy.
• History of seizure disorder
• Comorbid bipolar disorder, psychosis, organic mental disorder, or developmental disorder
• If there is a history of substance abuse, patients in remission at least 6 months.
• Currently being treated with behavioral therapy, specifically exposure and response prevention, for OCD.
• Other medications for medical disorders that may interfere with escitalopram
• Current major depression or prescribed an antidepressant for major depression within the past 12 months.
• Taken an SSRI medication within 2 weeks of beginning the study (4 weeks for fluoxetine).
• More than 1 adequate trial (at least 10 weeks at maximally tolerated dose) with another SSRI in the past.