For people ages 18-65
A) OCD participants inclusion criteria:
- DSM-5 diagnostic criteria for OCD as primary (most severe) diagnosis (based on the Mini International Neuropsychiatric Interview).
- Yale-Brown Obsessive-Compulsive Scale (YBOCS) total score is equal or greater than 16.
- unmediated or being on a stable dose of medication (only SSRIs and clomipramine) for at least 12 weeks prior to the study.
- fluent English speaker.
- signed informed consent.
B) OCD participants exclusion criteria:
- IQ greater than 80 on the Wechsler Abbreviated Scales of Intelligence.
- lifetime DSM-5 diagnosis of mania, psychotic disorder, or substance dependence (per MINI).
- current DSM-5 diagnosis of MDD if Montgomery-Asberg Depression Scale (MADRS) scores are equal or greater than 35 (severe), or ADHD.
- taking any psychotropic medication other than SSRIs or clomipramine.
- severe psychiatric symptom that requires immediate inpatient psychiatric intervention such as suicidality.
- presence of any serious psychiatric, psychosocial, or neurological condition requiring immediate treatment.
C) Healthy control inclusion criteria:
1-males and females age 18-65 years with signed informed consent and IQ greater than 80 on WASI.
D) Exclusion criteria for all participants:
- presence of any MR scan contraindications particularly body metal or positive pregnancy test.
- medical conditions in which cerebral metabolism might be compromised such as thyroid disorders, diabetes or current tobacco smoking (potential effect on imaging endpoints).
- any history of seizure disorders.