Deep brain stimulation (DBS) of the nucleus accumbens in treatment-refractory patients with obsessive-compulsive disorder (OCD).

1. Primary diagnosis: OCD (300.3) according to DSM-IV criteria using the MINI Plus-interview as diagnostic instrument;

2. Illness duration > 5 years;

3. Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) total > 27, measured twice at least two weeks apart;

4. Disabling severity with substantial funtional impairment according to the DSM-IV criterion C and a Global Assessment of Function (GAF) score of <45;

5. Age 18 - 65 years;

6. Written informed consent;

7. Able to fully understand the consequences of the procedure (IQ>80);

8. Dutch speaking and able to answer all study questions;

9. Capable to make his or her own choice without coercion;

10. Treatment refractory is defined as no or insufficient response (still fulfilling the inclusion criteria) following:

a. Two treatments with a SSRI at maximum dose for and least 12 weeks, and

b. One treatment with clomipramine at the maximum dose for at least 12 weeks, with assessment of clomipramine/desmethylclomipramine plasma levels to control for sufficient bioavailability, and

c. At least one augmentation trial with an atypical antipsychotic for 8 weeks in combination with a SSRI, and

d. At least one (cognitive) behaviour therapy trial for 16 weeks in combination with an effective drug for the treatment of OCD.

Any of the following: unstable physical condition, Parkinson's disease, dementia, epilepsy, schizophrenia or history of psychosis, alcohol or substance abuse during last 6 months, current tic disorder, antisocial personality disorder, body dismorphic disorder, pregnancy, use of psychiatric medication other than: stable use of one SSRI or clomipramine, one benzodiazepine, one atypical antipsychotic.