It all started with a three-minute video my pelvic floor physical therapist friend uploaded to her practice’s YouTube channel. In it, she attaches a TENS unit to her ear in an effort to stimulate the vagus nerve for stress reduction and calming effects. “What?” was my initial thought. A week later, I saw an Instagram reel about humming (yes, humming) for a “vagus nerve reset” to calm down the body. While stress reduction is relevant to both men and women, women are disproportionately affected by anxiety and depression. Interestingly enough, an informal poll of my social media contacts suggests that only my female friends were seeing “vagus nerve reset” content in their algorithms.
My only previous reference point for the vagus nerve was from nursing school fifteen years ago, and the single thing I remembered was that the vagus nerve innervates the diaphragm, meaning that it influences its contraction and expansion.
How could all these things be connected, I wondered, and (knowing the pitfalls of our digital age) what was fact versus fiction? Here’s what I’ve since learned about the vagus nerve, including what most health and wellness influencers get wrong about its function, and how stimulating it might actually help a wide variety of health conditions, including all the most common causes of death.
What is the vagus nerve?
We’ve all heard of nervous system regulation (or dysregulation), and terms like “fight or flight response” (and even more recently, ‘“fight, flight, freeze, or fawn response”) and “sympathetic nervous system” are rapidly imprinting on our cultural lexicon to, arguably, the same extent as “the mitochondria is the powerhouse of the cell,” (the oft-repeated phrase most of us learned in fifth grade).
But from a more precise biological perspective, let’s recall that the nervous system comprises our brain, spinal cord, and nerves that send and receive signals all throughout our body, including 12 pairs of cranial nerves that originate in the brain. The cranial nerves transmit sensory information or motor information to and from the brain. The vagus nerve is cranial nerve 10. Like I wrote above, since each cranial nerve is paired, there are actually two vagus nerves, one on either side of the neck.
In Stanford neuroscientist Andrew Huberman’s podcast episode on the vagus nerve, he noted, “We’re talking about a nerve of many, many different pathways that both receives and provides information from essentially all areas of the body down to the base of your pelvis.”
Here’s why the vagus nerve is special
Huberman differentiated the vagus nerve’s function from the function of all the other cranial nerves, continuing, “And that stands in direct contrast to the other cranial nerves, which tend to receive information from restricted areas of the body, most specifically the head and neck areas, and tend to provide connections to the head and neck area.”
Most health and wellness influencers miss this key point about vagus nerve function
After clarifying that his goal isn’t to throw shade on health and wellness influencers or your local yoga instructor, Huberman explained, “Most of the time when you hear about the vagus nerve out there in the general world… it’s about the vagus nerve being a ‘calming pathway’ that’s involved in transmitting information about the sensory milieu of the body—so, you know, heart rate, acidity of the gut, how comfortable we are in our body—to our brain. And people will say, ‘You want to activate the vagus nerve because you want to calm down.’”
Huberman affirmed, “Well, that is true,” before clarifying, “but it’s just one small fraction of the functions of the vagus nerve.”
The vagus nerve has both sensory and motor functions
This is because, Huberman elaborated, “The vagus nerve is both a sensory pathway and a motor pathway” (emphasis added). While it is true, as the influencers attest, that “a ton of sensory information is coursing up from the organs of the body into the brain, through what we call the vagus nerve, there’s also motor information coming from the brain to the body.”
This matters because “it turns out that if you want to access the calming aspects of vagus nerve activation, versus the energizing effects of vagus nerve activation, versus the immune enhancing effects of vagus nerve activation, versus the ways that you can improve learning using vagus nerve activation, you need to know whether or not you’re trying to activate a sensory pathway or a motor pathway within this vast set of connections that we call the vagus nerve” (emphasis added).
“It turns out that if you want to access the calming aspects of vagus nerve activation, versus the energizing effects of vagus nerve activation, versus the immune enhancing effects of vagus nerve activation, versus the ways that you can improve learning using vagus nerve activation, you need to know whether or not you’re trying to activate a sensory pathway or a motor pathway within this vast set of connections that we call the vagus nerve”
As pioneering vagus nerve stimulation neuroresearcher Dr. Kevin Tracey explained in an op-ed, you have 100,000 nerve fibers in each vagus nerve: that’s 200,000 total. And every single one is technically a unique nerve. So the question we should ask when influencers or others who insist that they’re stimulating the vagus nerve via deep breathing, ice baths, humming, or something else, is ‘which one?’
How could the vagus nerve potentially impact so many different kinds of conditions?
I’ve written before about red light therapy, specifically answering the question of how one type of therapy could possibly offer hope for the treatment of a whole variety of conditions, some of them with little to no obvious connection, overlap, or crossover. In that article, I wrote, “Turns out that when you help your cells’ mitochondria work smarter, not harder, you experience reduced inflammation and faster injury, wound, or other tissue healing. And those effects happen to impact many, many modern health conditions.”
If we zero in on one word from that quote, we get the answer to why vagus nerve stimulation appears to have equally disparate potential benefits.
That word is inflammation.
Vagus nerve stimulation triggers the inflammatory reflex
Stimulating the vagus nerve, Dr. Tracey noted, appears to trigger the inflammatory reflex, which down-regulates the effect of pro-inflammatory cytokines in the body. We’ve all heard that inflammation is directly related to the most common illnesses that plague modern man. In a wide-ranging, two-plus-hour-long interview (the transcript is here!) on the Tim Ferriss show, Dr. Tracey connected the dots between inflammation and the current top causes of death.
Stimulating the vagus nerve, Dr. Tracey noted, appears to trigger the inflammatory reflex, which down-regulates the effect of pro-inflammatory cytokines in the body.
He said, “60 million people die on the planet Earth every year. And 40 million of them die from heart disease, stroke, neurodegeneration, Alzheimer’s, Parkinson’s, metabolic syndrome, diabetes, and cancer. So two thirds of the people that die every year on the planet Earth die of those conditions. And that’s according to the WHO [World Health Organization]. Those conditions all have one thing in common: they’re either caused by inflammation or made worse by inflammation.”
This may explain how you can hear about the proven effects of cranial nerve stimulation for chronic pain, as well as treatment-resistant epilepsy and depression, stroke, migraine, and even mood regulation and improved learning in healthy individuals.
But not every technique or hack that purports to stimulate the vagus nerve is in fact doing that. The vagus nerve stimulation benefits with robust research backing are directly and specifically related to FDA-approved implanted vagus nerve stimulation devices, particularly for treatment-resistant epilepsy and depression (the company Dr. Kevin Tracey co-founded, SetPoint Medical, recently got FDA clearance for implanted vagus nerve stimulation to treat a third condition, rheumatoid arthritis).
As both Huberman and Tracey stressed, viral life hacks to create more calm or help you stress less rely on a very imprecise understanding of the complexities of what the vagus nerve is and does. Of course, just because we don’t understand something well (or at all) doesn’t mean it can’t work. Or it may work in a different way than we thought.
As both Huberman and Tracey stressed, viral life hacks to create more calm or help you stress less rely on a very imprecise understanding of the complexities of what the vagus nerve is and does. Of course, just because we don’t understand something well (or at all) doesn’t mean it can’t work.
Noninvasive methods shouldn’t be considered vagus nerve stimulation
As an example, Dr. Tracey noted that research into non-invasive transcutaneous electrical nerve stimulation (transcutaneous, as it transmits electrical impulses through the skin)—like my pelvic floor physical therapist friend was advocating—isn’t specifically or directly stimulating the vagus nerve. While my friend was attaching the TENS unit to the tragus of her ear, Dr. Tracey noted that in research he and his team conducted based on known principles of auricular acupuncture, a branch of the vagus nerve goes to a slightly different part of the ear, the cartilage tissue in the cymba concha.
Tracey said, “It’s the only place that the vagus nerve endings go to the surface of the skin, and they are sensory.” At most, with TENS unit use on the correct part of the ear, you are stimulating a branch of the vagus nerve, not hitting “the big cable.”
This doesn’t mean there cannot be beneficial effects of TENS unit use on other parts of the ear besides the cymba concha. In fact, a 2023 meta-analysis and systematic review of two non-invasive forms of transcutaneous “vagus nerve stimulation” found that cervical or ear stimulation may be a safe, cost-effective way to boost the effectiveness of migraine medication [1]. (See study for specifics on reduction of migraine pain versus migraine prevention/having fewer migraine or headache episodes.) Though these methods would not directly stimulate the vagus nerve, as explained by Tracey, they may still be effective for reasons we don’t quite understand. And in fact, according to Tracey’s book, The Great Nerve, auricular TENS unit use has been found beneficial for epilepsy, depression, anxiety, pain, opioid withdrawal, and more (Tracey, 163).
What does all this mean for ice baths, TENS unit use, and deep breathing?
How do we make sense of Dr. Tracey’s research, Andrew Huberman’s explanations, and the calming hacks promoted by your health and wellness influencer of choice or local yoga teacher? Both Tracey and Huberman affirmed that we have much to learn when it comes to capitalizing on the health benefits of vagus nerve stimulation, especially drilling down to what the individual fibers of the vagus nerve do and how they work together. Tracey further stressed that it’s difficult to prove through scientific research some of the observed pluses of various techniques that seem to (indirectly) affect the vagus nerve. In addition, it is not possible to directly scientifically measure the supposed benefits of vagus nerve stimulation.
Still, Dr. Tracey acknowledged that he engages in four daily practices that may indirectly affect the vagus nerve. They include breathwork, meditation, cold water exposure, and regular exercise. Though we don’t know exactly how each of these may trigger the inflammatory reflex that the body uses to tamp down runaway inflammation, they’ve been proven to enhance our health and ability to cope with or prevent disease.
Still, Dr. Tracey acknowledged that he engages in four daily practices that may indirectly affect the vagus nerve. They include breathwork, meditation, cold water exposure, and regular exercise. Though we don’t know exactly how each of these may trigger the inflammatory reflex that the body uses to tamp down runaway inflammation, they’ve been proven to enhance our health and ability to cope with or prevent disease.
At the end of the day, the viral calming hacks you see online aren’t likely to harm you, but, given the wide-ranging and far-flung functions of the vagus nerve, they may not put you into a zen state either. Tracey hopes that those who try a hack intended to stimulate the vagus nerve and find it wanting will recognize that this doesn’t discredit the proven effects of implanted vagus nerve stimulation.
References
[1] Song D, Li P, Wang Y, Cao J. Noninvasive vagus nerve stimulation for migraine: a systematic review and meta-analysis of randomized controlled trials. Front Neurol. 2023 May 11;14:1190062. doi: 10.3389/fneur.2023.1190062. PMID: 37251233; PMCID: PMC10213755.
