Pivotal Trial (D02) of Vagus Nerve Stimulation (VNS) for Treatment-Resistant Depression (TRD)

Inclusion Criteria: 1. diagnosed with major depressive episode (MDE) 2. chronic (\>=2 years)or recurrent (\>-=4) lifetime MDEs 3. resistant to \>=2 treatments from different categories 4. completed \>=6 weeks of psychotherapy 5. score \>=20 on 24-item Hamilton Rating Scale of Depression 6. IQ \>=70 7. stable on current antidepressant medication (no more than 5 antidepressant meds) or taking no antidepressant meds for \>=4 weeks before Visit B1 8. stable on atypical antipsychotic and anticonvulsant medications as for item #7 9. age \>=18 amd \<=80 years 10. male or nonpregnant female adequately protected from conception. 11. able to comply with testing and follow-up visits 12. voluntarily signed informed consent 13. patients with bipolar disorder demonstrated a resistance to lithium treatment or has a medical contraindication to treatment with lithium or is known to be intolerant to lithium (not applicable to patients with MDD) Exclusion Criteria: 1. atypical depression at study entry or psychotic symptoms in any MDE 2. history of schizophrenia, schizoaffective disorder, or delusional disorders 3. rapid cycling bopolar disorder 4. secondary diagnosis of, or signs of, delirium, dementia, amnestic, or other cognitive disorders 5. failed 7 or more antidepressant treatments 6. a. suicide attempt requiring medical attention within previous 12 months b. \>=2 suicide attempts in the past 12 months c. cannot guarantee that will not implement suicide d. likely to attempt suicide within next 6 mon in investigator's opinion 7. alcohol or substance dependence within previous 12 months or abuse within previous 6 mon other than nicotine dependence or abuse 8. history of myocardial infarction or cardiac arrest 9. other progressive neurological disease, significant central nervous system disease or injury, or cervical fracture that makes implantation difficult 10. received general anesthesia with 390 days before enrollment. 11. taken an investigational drug within a clearance duration of 5 x the half-life of the investigational drug or within \<=4weeks before Visit B1, whichever time is greater 12. enrolled in another investigational study 13. using another investigational device 14. significant cardiac or pulmonary condition currently under treatment resulting in an ASA score \>=III 15. history of, or evidence of, significant brain malformation or significant head injury or clinically apparent cerebral vascular events, or prior brain surgery such as cingulatomy 16. unilateral or bilateral cervical vagotomy 17. demand cardiac pacemaker, implantable defibrillator, or other implantable stimulator 18. likely to require a whole body MRI after NCP implantation 19. currently receiving or likely to receive short-wave diathermy, microwave diathermy, or therapeutic ultrasound diathermy after implantation 20. plans to relocate or move to a location distant from the study site within one year of enrollment 21. previously enrolled in this or any other NCP System study -