VNS received FDA approval for the adjunctive (add-on) treatment of resistant depression in 2005; prior to this, its only use was in the treatment of epilepsy. VNS involves the surgical implantation of an electrical device that stimulates the vagus nerve, a complex nerve that originates in the brain, travels down the neck and influences a number of critical functions in the body, including heart rate and sweating to how quickly food passes through our digestive systems.
Implantation of the pocketwatch-sized device in the upper left chest is done under general anesthesia. Once implanted, the device delivers a current at regular intervals. The results of studies looking at VNS were not robust, less than a 30 percent success rate. Still it does offer an option and some hope to people with severe and recurrent depression, where nothing else has worked.
Like other antidepressant treatments, VNS can cause a switch to a manic, mixed, or hypomanic episode. The role of VNS in the treatment of bipolar disorder (especially bipolar depression) has not been well studied.
VNS carries the risks of the surgery and general anesthesia. Other complications that have been reported include damage to the vocal cords and damage to the nerves that control feeling in the lower portion of the face.