How Hormones and Exposure and Response Prevention (EX/RP) Affect the Brain of People With OCD

Inclusion Criteria:

1. Diagnostic and Statistical Manual of Mental Disorders (DSM-5) Diagnosis of OCD;

2. Male and female subjects aged between 18- 45;

3. Women must be menstruating and regularly cycling

4. Ability to tolerate a treatment-free period;

5. No psychotropic medication in the past 12 weeks

6. At entry, at least moderate severity OCD

7. Willingness and ability to give written informed consent after full explanation ofstudy procedures.

Exclusion Criteria:

1. Use of birth control (oral contraception or IUD) that affects the menstrual cycle,or menopause.

2. Pregnancy. Women of childbearing potential will be required to sign a statementindicating their intention to avoid pregnancy during the study.

3. Neurologic or medical condition that would prevent safe participation in the fullstudy protocol.

4. Any contradiction to magnetic resonance imaging (e.g., metallic implants ordevices).

5. Comorbid psychiatric conditions that significantly elevate the risks associated withstudy participation or confound results.

6. Patients with prominent suicidal ideation or with a recent suicide attempt.

7. Current psychotherapy