A Study to Assess Effectiveness and Efficiency of VNS Therapy in Patients With Difficult to Treat Depression.

This study is evaluating how well vagus nerve stimulation (VNS) — a small device implanted under the skin that sends mild electrical pulses to the brain — works for people with long-lasting or recurring severe depression that has not improved with multiple antidepressant treatments. **You may be eligible if...** - You are 18 or older - You have been diagnosed with chronic (more than 2 years) or recurring major depression - You have tried multiple antidepressant treatments without sufficient improvement - You are willing to give written consent **You may NOT be eligible if...** - Your depression is secondary to another medical condition - You have had a previous VNS device implanted - You have conditions that make surgery or the device unsafe (e.g., certain heart conditions) - You have bipolar disorder or psychosis Talk to your doctor to see if this trial is right for you.