Deep brain stimulation for treatment resistant deep brain stimulation

Subjects will receive bilateral deep brain stimulation to the ventral capsule/ventral striatum. They will receive standard follow-up and device programming over the span of 52 weeks. After that, they will enter a 5 week double blinded crossover phase consisting of 2 weeks of ON or OFF stimulation, separated by 1 week of 'washout', during which stimulation will be OFF.

Inclusion Criteria:

1. Female or Male patients between age 18-70

2. DSM-V diagnosis of Obsessive Compulsive Disorder (OCD), at least 5-year illness history with a minimum score of 24 on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS).

3. SF-36<40

4. Medication-refractoriness as determined by an adequate dose and duration of psychiatric treatments (including psychotherapy and/or pharmacology) as determined by two psychiatrists associated with the study. Including specifically:

   1. Failed adequate trial of two or more medications accepted as first line in the treatment of OCD
   2. Attempted augmentation, if tolerated, by at least 1 medications known to be first line treatments for OCD

5. An adequate trial of cognitive behavioural therapy

6. Ability to provide informed consent and comply with all testing, follow-ups and study appointments and protocols

Exclusion Criteria:

1. Any past or current evidence of psychosis or mania (patients with co-morbid depression will not be excluded from the study)
2. Active neurologic disease, such as epilepsy
3. Alcohol or substance dependence or abuse in the last 6 months, excluding caffeine and nicotine
4. Current suicidal ideation
5. Any contraindication to MRI scanning
6. No contraindication for DBS surgery
7. Presence of significant cognitive impairment
8. Likely to relocate or move out of the country during the study's duration
9. Presence of clinical and/or neurological conditions that may significantly increase the risk of the surgical procedure.
10. Currently pregnant (as determined by history and serum HCG) or lactating; for females of reproductive potential: use of highly effective contraception for at least 1 month prior to screening and agreement to use such a method during study participation

An independent member of the study team will perform the randomization and programming, allow for care givers, participants, investigator, and outcomes assessors to be blinded.