This study is looking at how effective and safe a treatment called VNS Therapy® is for people with depression that hasn't improved with other treatments. VNS stands for Vagus Nerve Stimulation. It's done by implanting a device in the body that sends electrical signals to the brain. The study will compare people who get the VNS Therapy with those who don't get the stimulation, over 12 months. After a year, everyone in the study gets the therapy for a longer term to see how they do over time.

Eligibility: To join, you need to have been depressed for at least two years or have had at least four episodes of depression. You must have tried at least four treatments without success.

• The study lasts up to 5 years for some participants.
• Participants must visit the study center for assessments.
• There are specific risks and eligibility criteria to consider.