A Prospective, Multi-center, Randomized Controlled Blinded Trial Demonstrating the Safety and Effectiveness of VNS Therapy® System as Adjunctive Therapy Versus a No Stimulation Control in Subjects With Treatment-Resistant Depression

Inclusion Criteria: The patient must be in a major depressive disorder (MDD) episode for ≥ two years or have had at least four episodes of MDD, including the current episode. The patient's depressive illness meets a minimum criterion of four prior failed treatments of adequate dose and duration as measured by a tool designed for this purpose. The patient is experiencing a major depressive episode (MDE) as measured by a guideline recommended depression scale assessment tool on two visits, within a 45-day span prior to implantation of the VNS device. Patients must maintain a stable medication regimen for at least four weeks before device implantation. Exclusion Criteria: Current or lifetime history of psychotic features in any MDE; Current or lifetime history of schizophrenia or schizoaffective disorder; Current or lifetime history of any other psychotic disorder; Current or lifetime history of rapid cycling bipolar disorder; Current secondary diagnosis of delirium, dementia, amnesia, or other cognitive disorder; Current suicidal intent; or Treatment with another investigational device or investigational drugs.