Doctors aren't exactly sure why vagus nerve stimulation (sometimes called vagal nerve stimulation) can be effective in treating depression [source: WebMD]. However, anecdotal evidence suggests that the impulses, by stimulating the brain stem, can affect the chemical balance of the mood centers of the brain and enhance the production of neurotransmitters, which have been shown to ease some depression symptoms [sources: AANS; Mayo Clinic].
Shortly after the U.S. Food and Drug Administration (FDA) approved the use of VNS for the treatment of epilepsy in 1997, researchers began to notice that the treatment showed signs of promise in treating some epileptic patients who also suffered from depression. Studies revealed little improvement after several months but a significant benefit after a year of treatments.
Based on those studies, the FDA approved VNS treatment for depression in 2005, under the very strict guidelines mentioned earlier. However, even with rigid criteria in place, the use of VNS is still somewhat controversial -- given the lack of long-term findings and uncertainty of side effects -- and is not currently covered by Medicaid.
That can be a daunting issue for patients already dealing with depression, as the initial cost of implanting a VNS device can run more than $30,000. Which doesn't include subsequent visits for monitoring and adjustments. Some private health insurers will cover some or part of this cost, but they are in the minority. Ask beforehand to avoid surprises.
Also, since vagus nerve stimulation is a relatively new depression treatment, candidates are encouraged to carefully consider the pros and cons before using it [source: Mayo Clinic]. Patients are also required to continue standard depression treatments along with VNS. According to the AANS, however, VNS should not be considered for any patient suffering from acute suicidal thoughts or behavior, schizophrenia, delusional disorders or history of rapid cycling bipolar disorder.