The device is implanted in the chest and sends impulses to the brain through a nerve in the neck.
FDA officials cautioned that the VNS device is not to be used as the first therapy but would give the sickest patients another option.
"We're really dealing with a very sick group of patients here. These are not standard depression patients," said Dr. Daniel Schultz, director of the FDA's device center.
The device would carry the strongest warning possible -- a so-called black box -- cautioning patients that the device is permanent, Schultz said in an interview.
Cyberonics will also have to create a registry to monitor some patients.
