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.