Vagus Nerve Stimulation

Early experiments and the first implanted device

A 2003 review reports that neuroscientists speculated early in the 20th century that stimulating the vagus nerve in the neck might alter brain activity, and that animal studies pointed in that direction. It credits Zabara with finding in the 1980s that stimulation reduced or eliminated seizures in dogs, which led to an implantable device for people. By 2003 the authors described the device as an accepted long-term epilepsy treatment used by more than 15,000 patients worldwide.

The U.S. Food and Drug Administration (FDA) database lists the original approval of the NeuroCybernetic Prosthesis System, filed as an implanted autonomic nerve stimulator for epilepsy, with a decision date of 16 July 1997. The database page does not state the labeled age range or seizure type, so those details are not given here.

Extension to depression and stroke rehabilitation

A historical review states that mood effects were noticed during the 1990s epilepsy trials, and that these observations led to approval of VNS for depression in 2005. The FDA record gives the decision date as 15 July 2005 and describes the indication as adjunctive long-term treatment for people aged 18 or older in a major depressive episode who have not responded adequately to four or more antidepressant treatments.

A 2022 report from the stroke trial states that a paired VNS and rehabilitation system was approved by the FDA in 2021 for chronic ischemic stroke survivors with moderate to severe arm and hand impairment. The same report says vagus nerve stimulators had by then been implanted in over 125,000 people with treatment-resistant epilepsy.

Non-invasive devices and popular claims

The historical review links the recent revival of interest in VNS partly to transcutaneous auricular devices, which apply stimulation through the skin of the ear. A 2022 specialist review adds that such devices were developed over recent years. The sources opened for this page do not trace the origin of popular wellness claims about stimulating the vagus nerve through breathing, cold exposure or humming, and no dated account of those claims is given.

One phrase, three different things

In clinical literature, vagus nerve stimulation (VNS) usually means an implanted pulse generator connected to an electrode on the nerve in the neck, sometimes called invasive or implanted VNS. Transcutaneous VNS (tVNS) means stimulation through the skin, and transcutaneous auricular VNS (taVNS) means stimulation at the outer ear. These are different devices with separate evidence, and findings for one are not findings for another.

In popular wellness writing the phrase is also applied to self-directed practices such as voluntary slow breathing, which involve no device. Researchers studying such practices commonly measure vagally-mediated heart rate variability (vmHRV), a heart-rhythm index treated as a marker of parasympathetic activity. A separate Machipedia page covers Polyvagal-Informed Therapy, and polyvagal theory is not described here.

Clinical terms used in the trials

Epilepsy trials describe high-level and low-level stimulation, where the lower level served as a comparison. Depression trials use treatment-resistant for people whose illness has not responded to several adequate treatments; the 2024 sham-controlled trial enrolled adults with at least four unsuccessful treatments in the current episode. Closed-loop systems, which respond to a heart-rate change linked to a seizure, are described in one review as a newer generator design.

Implanted systems

A Cochrane review describes implanted VNS as chronic, intermittent electrical stimulation of the vagus nerve delivered by a programmable pulse generator. In the stroke rehabilitation trial, all participants were implanted in an outpatient procedure and were discharged within 48 hours. Rehabilitation therapy began roughly 10 days later, and stimulation was paired with the therapy movements during in-clinic sessions over six weeks, followed by a home exercise program.

Clinicians adjust settings after implantation, and reviews note that side effects can often be managed by changing the stimulation parameters. This page does not describe settings or procedures.

Transcutaneous devices

Transcutaneous devices apply electrodes to the skin. Studies of ear-based stimulation for functional dyspepsia used the concha and tragus of the ear. A specialist review notes that these stimulators must be applied by the user, are active only intermittently, and that adherence is uncertain, in contrast to an implanted system that runs continuously.

Self-directed breathing practices

Voluntary slow breathing is a self-directed practice with no device or procedure. A 2022 meta-analysis pooled 223 studies of slow breathing and measured heart rate variability during sessions, immediately afterward and after multi-session programs. The practice is mentioned here because it is often called vagus nerve stimulation in popular writing; the review itself does not describe it as nerve stimulation.

Approved clinical indications for implanted VNS

Implanted VNS is used as an add-on treatment for drug-resistant epilepsy in adults and children, per the Cochrane review. The FDA indication for depression is adjunctive long-term treatment of chronic or recurrent depression in adults who have not responded adequately to four or more antidepressant treatments. A paired VNS and rehabilitation system was approved in 2021 for chronic ischemic stroke survivors with moderate to severe arm and hand impairment.

Investigational uses of transcutaneous devices

Transcutaneous auricular stimulation has been studied in research settings for conditions including functional dyspepsia and depression. Authors of a 2026 trial protocol describe the depression application as experimental because high-quality evidence is limited and the mechanisms are unclear. A specialist review lists tinnitus, headache and gastrointestinal complaints among uses for which studies confirming effectiveness are missing.

Popular wellness claims

Voluntary slow breathing is described by researchers as a technique used to support physical and mental well-being on the assumption that it influences the parasympathetic nervous system. The sources reviewed did not document specific claims made for consumer devices, cold exposure, humming or other exercises, and no evidence for those claims is reported on this page.

Implanted VNS for drug-resistant epilepsy

The 2022 Cochrane review included five randomized trials with 439 participants with drug-resistant focal seizures. Four trials compared high with low stimulation: the risk ratio for a 50 percent or greater seizure reduction was 1.73 (95% CI 1.13 to 2.64), moderate-certainty evidence. The comparison was between stimulation levels, not stimulation against none, and blinding was difficult because voice changes revealed the active setting. A specialist review states the chance of complete seizure freedom is low and VNS is palliative.

Implanted VNS for treatment-resistant depression

A 12-month double-blind trial randomized 493 adults with marked treatment-resistant depression to active or no-stimulation sham VNS added to usual care. The primary outcome, percent time in response on the MADRS clinician scale, did not distinguish the groups. Some secondary clinician and patient ratings favored active VNS. Several authors work for the manufacturer, and the trial's own conclusion of benefit rests on secondary measures.

Implanted VNS paired with stroke rehabilitation

The VNS-REHAB trial randomized 108 people at least 9 months after ischemic stroke to rehabilitation with active or sham stimulation. Mean arm-function scores (Fugl-Meyer upper extremity) rose by 5.0 points with active stimulation versus 2.4 with sham, a difference of 2.6 (95% CI 1.0 to 4.2). At 90 days, 47 percent versus 24 percent had a clinically meaningful response. The manufacturer funded the trial, and it does not address acute stroke.

Transcutaneous devices

A 2025 meta-analysis of six sham-controlled trials (716 participants) of ear-based stimulation for functional dyspepsia reported improved symptoms with moderate-certainty evidence. That result applies to that condition alone. For depression, trial authors describe tVNS as experimental, and a specialist review judges non-invasive devices less effective than implanted ones for seizures and depression, with high-quality studies missing.

Slow breathing and heart rate variability

The 2022 meta-analysis of 223 studies found increases in vagally-mediated heart rate variability during slow breathing, immediately after one session and after multi-session programs. This measures a heart-rhythm index in a mixed set of studies. It does not show stimulation of the nerve, and it does not by itself show benefit for any condition.

Implanted VNS: stimulation effects and sleep apnea

The Cochrane review lists hoarseness, cough, dyspnea (breathlessness), pain, paresthesia, nausea and headache. Hoarseness (risk ratio 2.17, 99% CI 1.49 to 3.17) and dyspnea (2.45, 99% CI 1.07 to 5.60) were more likely with higher stimulation; certainty was moderate to low. The 2024 depression trial also found more dyspnea with active VNS. A specialist review says effects often lessen over years and that VNS may worsen existing sleep apnea.

Surgery-related events

In the stroke trial, one serious surgery-related event occurred, vocal cord paresis, in the control group; it eventually resolved. Participants were mostly taking antiplatelet or anticoagulant drugs, which were temporarily withheld around surgery, and no events were attributed to withholding them. These findings come from one trial population and may not apply to others.

Transcutaneous devices

A systematic review of 51 research studies with 1,322 participants found local skin irritation from electrodes in 18.2 percent, headache in 3.6 percent and nasopharyngitis in 1.7 percent. About 2.6 percent withdrew because of side effects, and 30 serious adverse events occurred, 3 judged possibly related. These data come from research settings, and the sources reviewed do not report harms of consumer devices.

Care boundaries and gaps in the sources

A specialist review states implanted VNS is palliative, usually requires continuing other treatment, and does not replace it. Slow breathing reviews report few adverse effects expected, which is the authors' judgment. A full list of labeled contraindications was not available in the sources opened, so it should be read in current manufacturer labeling and discussed with a treating clinician.