The vagus nerve is the longest cranial nerve. It runs from your brain all the way to your abdomen, going through your face and thorax along the way. Although we refer to it in the singular, it’s actually two different nerves – the left and the right vagus nerves. Each of these is composed of parasympathetic nerve fibers, with groups of nerve tissues that innervate different areas, such as the ears, neck, pharynx, and larynx. There are also esophageal, cardiac, pulmonary, and digestive tract branches. Vagus nerve stimulation can therefore have an effect on all of these areas, as we’ll see in more detail in this article.
When we talk about the parasympathetic effects of the vagus nerve, we’re referring to the two main branches of the autonomic nervous system (ANS): the sympathetic nervous system (SNS) and parasympathetic nervous system (PNS).
Your ANS is the part of your nervous system that functions without your conscious control. It’s what keeps your heart beating, lungs breathing, blood circulating, and gastrointestinal tract digesting. Its SNS branch has to do with alertness and the “fight or flight” response. It’s responsible for helping you deal with a threat and gives you the energy and alertness you need to survive danger. Your PNS, on the other hand, is what helps your body return to resting and digesting once the threat has passed.
The vagus nerve, being part of the PNS, is therefore an important element in helping your body get back to a relaxed state. If you have a vagal imbalance or insufficiency, then you may have more trouble returning to the relaxed parasympathetic state, and you may also be more susceptible to being chronically on overdrive in the sympathetic state.
Before we can comfortably discuss how the vagus nerve works and its role in neurological and psychiatric conditions, it’s important to understand the different nervous system cells involved in the communication of your nervous system.
The first are neurons. Neurons are the cells that carry signals throughout your nervous system, either electrically or chemically through the use of neurotransmitters. Your CNS comprises your brain and spinal cord, while your peripheral nervous system comprises all the nerve fibers that branch out to and from the rest of your body, including your extremities. Neurons carry orders from your CNS to peripheral muscles, organs, and systems. They also report back to the brain and CNS what’s happening in those areas.
Your vagus nerve serves as a link between your CNS and a specific part of your peripheral nervous system – your enteric nervous system (ENS). The ENS is your gut’s nervous system, and it plays an important role in the communication between your gut and brain.
The other type of nervous system cell is the glia. Glial cells support neurons, and they come in different types. Astrocytes help nurse neurons and supply them with nutrients from the vascular system. Oligodendrocytes are what myelinate neurons, forming a protective sheath around their axons that also helps electrical signals pass through them more quickly. Microglia are the nervous system’s immune cells, and it's important to know that they can be in a patrolling, reactive, or restorative state.
Glial cells outnumber neurons, and though they mainly play supportive roles to neurons, they play a big part in neuroinflammation, which is something that non-invasive vagus nerve stimulation aims to resolve.
As the PNS’s main component, the vagus nerve is responsible for creating a state of relaxation in the organs and systems it affects. For example:
On the other hand, when you’re in the sympathetic state, the opposite of these effects occurs. Your heart rate and blood pressure increase and your digestion is not prioritized. You need the energy that would have gone to digestion for the “fight or flight” response instead. But in the parasympathetic relaxed state, a lot more of your energy can be allocated for digestion and other critical processes.
The vagus nerve’s esophageal branches help to control the esophagus, stomach, and intestinal muscles in order to create peristalsis. Peristalsis is the wave-like movement of your gastrointestinal muscles that helps food move through. This branch of the vagus nerve is also responsible for digestive secretions, such as bile and digestive enzymes.
This is just one aspect of the complex interconnectedness between your brain and gastrointestinal system. The gut-brain connection, for example, is becoming more and more apparent in research and has a much bigger role in neurological and psychiatric conditions than previously thought. Still, the exact mechanism of that connection is not yet completely clear. What we do know, however, is the following.
Your ENS is the largest component of your ANS, with between 200-600 million neurons. And because of this, healthcare practitioners sometimes call it “the second brain.” The ENS can actually regulate itself and doesn’t require the involvement of your CNS to function. Your ENS does, however, communicate with your brain, and vice versa.
You might be surprised to learn just how much the gut and the brain are connected, but if you think of it in terms of survival and evolution, it makes sense. First of all, there is research that suggests that your CNS and ENS developed from the same embryonic tissue.
Secondly, one of the biggest interfaces we have with the external world is through the gastrointestinal (GI) tract. We take in food and water through there several times a day, and it is the internal part of the body most exposed to the environment. Many unwanted substances, such as pathogens and toxins, can enter your system through there.
That’s why two-thirds of your immune system cells are in your gut, in what’s called the gut-associated lymphoid tissue (GALT).
Your immune system has to be able to respond quickly and powerfully if a pathogen or toxin enters your system through your GI tract. That immune response will create acute inflammation to help get rid of that unwanted invader and also any dead or damaged cells.
The inflammatory cytokines produced in the gut act as chemical messengers between the cells and tell the rest of your nervous system what’s going on. They help direct the immune cells to the correct destination. If these cytokines travel from your gut to your brain, they create neuroinflammation there and active your microglia, which are the resident macrophages of your CNS.
Also, the neurons of your ENS tell your brain and CNS that there’s something going on in your GI tract. That way, the rest of your system can support the process of ridding your body of whatever invader entered. For example, if the neurons determine that you’ve ingested bad food and then send that message to your CNS, your CNS will then trigger your GI tract to vomit or create diarrhea to get rid of it as quickly as possible. Around 90% of this two-way communication happens via your vagus nerve.
About three-quarters of your body’s neurotransmitters are made in the gut. Neurotransmitters are the chemical messengers that transmit signals between your neurons. Some are inhibitory, meaning they reduce the activation of your neurons, and some are excitatory, meaning they increase neuronal activation.
The fact that the majority of them are made in the GI tract means that the connection between your gut and your brain is extremely important for pretty much all your physiological functions - from immune health, to the stress response, to your body’s ability to return to a state of homeostasis. The CNS and ENS regulate this connection together, and if either of them dysregulates, that will affect the other.
This connection is also why you see those with GI tract disorders, such as irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD) suffering from anxiety and other mental health issues. The correlation between mood and the gut can no longer be denied or taken for granted. And one of the biggest players when it comes to this correlation is the health of your gut flora.
Adding to the gut-brain connection, there’s a third and quite important component: the gut’s microbiome. In fact, all three of these are part of the NeuroEndoMetabolic (NEM) Stress Response. The NEM is your body’s global response to stress, and it’s composed of six circuits of organs and systems, all of which work together to fight stress. They are the Hormone, the Bioenergetics, the Neuroaffect, the Cardionomic, the Inflammation, and the Detoxification circuits.
Each circuit is composed of three main components, and every two circuits share one component. That’s how the circuits are connected and form the NEM stress response network. The microbiome connects the Neuroaffect and Inflammation circuits. Later we'll discuss how inflammation and neurological and psychiatric conditions are linked.
The Neuroaffect Circuit is composed of your brain, ANS, and microbiome. And the Inflammation Circuit is composed of your gut, microbiome, and immune system. So far, we’ve covered the role of the brain, ANS, gut, and immune system. Now, let’s look at the microbiome’s role and then tie them all together.
A microbiome is a collection of microorganisms living together, including bacteria, fungi, and viruses. Your body is made up of more microbial cells than human cells. The genome of your body’s microbiomes is 100 times bigger than yours. And your body has different microbiomes, including the gut, skin, oral, and vaginal microbiomes.
Generally speaking, when we’re talking about the balance of a microbiome, we’re looking at the balance between the so-called good and bad bacteria. If you have enough good bacteria, in terms of numbers and diversity, then your microbiome is in balance. The good ones keep the bad ones in check. But an imbalance – a state called dysbiosis - indicates the harmful ones are taking over. And that can cause a lot of problems. When it comes to the vagus nerve, the most important microbiome to discuss is the gut microbiome.
Gut flora can actually not only affect your mood, they can also influence your thoughts, memories, and behavior. Dysbiosis is a major cause of chronic inflammation, which can then travel to the brain and nervous system, causing the microglia to get into a reactive state and the neurons to go into a defensive state. This hyperactivation has many consequences, some of which include issues with mental health, headaches, chronic pain, and even neurodegeneration.
Dysbiosis is a huge stressor on the body. And other forms of stress can trigger or worsen dysbiosis. In fact, stress has this bidirectional relationship with pretty much every condition we’ll mention in this article. And that has to do with what your body perceives as a stressor and how your body deals with stress.
A stressor can be any physical or psychological change or event that puts your body out of homeostasis. And there are healthy and unhealthy forms of stress. Exercise, for example, is a form of healthy stress in most cases. Acute stress, even if it’s from an unpleasant source, like conflict over a parking space or getting a cold, is usually not harmful because it doesn’t last. Chronic stress, however, is one of the most damaging things modern life has to offer.
Chronic stress causes your adrenal glands, which are your NEM’s first responders, to overwork. They have to produce more and more cortisol to meet the growing demand. Cortisol is your body’s main anti-stress hormone and it has many different functions, including regulating blood pressure and blood sugar levels, maintaining heart and blood vessel function, suppressing the immune system, and neutralizing inflammation.
A combination of stress and dysbiosis could not only compromise your gut’s lining, but also the permeability of your blood-brain-barrier (BBB). That’s the barrier that allows blood supplying nutrients to enter the brain but that also blocks off unwanted substances from entering.
A more permeable BBB can lead to more pathogens, toxins, and inflammatory cytokines reaching the brain and causing inflammation there, all the way from the gut. And this causes hyperactivation of the neurons and microglia, disrupting their homeostasis and their ability to repair and restore.
Chronic stress leads to adrenal fatigue, where your adrenals are no longer functioning optimally. The beginning stages of Adrenal Fatigue Syndrome (AFS) are characterized by elevated cortisol levels, while the later stages are characterized by a drop in cortisol production. Sometimes there is also dysregulation of the adrenaline and norepinephrine neurotransmitters, as these are also produced by the adrenals.
Symptoms of AFS include fatigue, weight gain, sleep disturbances, brain fog, anxiety, mild depression, hair loss, dry skin, PMS, infertility, loss of libido, hypoglycemia, salt and sugar cravings, lowered immunity, food and drug sensitivities, and heart palpitations.
When you have chronic stress, your ANS is consistently in the sympathetic state. So one thing that vagus nerve stimulation could help with is to induce a parasympathetic state to allow your body to rest and digest. Another way vagus nerve stimulation could help is by reducing the level of inflammatory cytokines, and inflammation, in your body. Inflammation is one of the biggest stressors on the adrenals and also something that is worsened by AFS.
Lastly, all of the conditions that vagus nerve stimulation improves are stressors in their own right. For example, chronic migraines are a source of stress and can easily dysregulate your NEM, as can many other chronic conditions.
On the flip side, vagus nerve stimulation should not be taken as an alternative to adrenal fatigue recovery or taking other steps to directly address chronic health problems. It should only be added as a complementary therapy. The core of adrenal fatigue recovery is a healthy diet, good sleep, stress management, gentle supplements, and appropriate forms of exercise. None of these can be replaced by acute therapies.
Vagus nerve stimulation has been around in some form or other since the 1880s. It started off with manual stimulation using massage, then moved on to more invasive methods using implanted devices. Now there are non-invasive devices that you can use at home.
We’ll now outline some of the interesting uses and effects of non-invasive vagus nerve stimulation for different conditions.
One study administered histamine to guinea pigs. Histamines are chemicals produced by the body in reaction to exposure to allergenic substances, such as pollen, or dust, or specific foods that you are allergic to. The histamines, and not the allergenic substance, are what cause the symptoms of allergic reactions, such as sneezing, coughing, or difficulty breathing. For example, that’s what causes your airways to constrict if you eat peanuts when you have a peanut allergy.
In this study, they stimulated the vagus nerves of these guinea pigs and saw a reduction in acute airway resistance.
A small pilot study in humans showed similar effects. Cervical, non-invasive vagus nerve stimulation reduced acute bronchoconstriction. This stimulation is given in the neck area. An interesting and unintended secondary effect was also reported by these participants: they experienced spontaneous relief of their headaches as well.
However, this makes sense because a lot of research shows there’s a very close association between asthma and migraines. And that brings us to the next, and possibly even more impactful, use of non-invasive vagus nerve stimulation.
Migraines affect approximately 15% of the global population. In the US alone, 36 million people suffer from them. They affect 18% of women and 6% of men, and they’re a huge burden economically and on the healthcare system.
Until now, their exact causes are not very clear. We do know that genetics plays a role, as do environmental factors. We also know that they affect the nerves and blood vessels in the head and brain. But migraines are not just a regular headache, they are a whole-body condition. Accompanying the pain, there could also be:
Some women also get menstrual migraines, which are associated with changes in hormone levels and can be aggravated by hormone imbalances, such as estrogen dominance. Cluster headaches, which are very painful and also on one side of the head, also seem to respond to vagus nerve stimulation.
One of the more frustrating aspects of migraine headaches is the difficulty in managing them. First of all, there is no cure, only strategies for prevention and management. With prevention, there are certain dietary and lifestyle factors that can help reduce the triggers that can lead to a migraine attack. Management usually consists of pain medications and rest, with as little exposure to stimulation as possible. However, this leaves is a big need for novel and holistic methods to relieve the often-debilitating effects of migraines.
Different studies have tested the effectiveness of cervical non-invasive vagus nerve stimulation for both the acute management of migraines as well as for migraine prevention. And the results are quite promising.
For acute therapy, different studies were conducted. One showed that cervical non-invasive vagus nerve stimulation led 12.7% of participants to be pain-free 30 minutes after the first attack of a migraine; 21% of them were free after 60 minutes, and over 30% of them were free of pain after 120 minutes. Compared to 4.2%, 10%, and 19.7% respectively for those who used a sham device, vagus nerve stimulation is more helpful in reducing the pain intensity.
With prevention, one study showed that close to 45% of participants had over 50% reduction in the number of days they experienced migraines. Another showed a 2-3 day/month reduction, and another showed 33% reduction in monthly days. Those are quite exciting results. They can make a huge difference in your quality of life if you have chronic migraines. They would also reduce your need for preventive or symptom-relief migraine medications.
One of the problematic things with current migraine care is that it is overly reliant on pain and nausea relieving medications. Of course, symptom relief is a very important part of care, and with something as painful and destabilizing as migraines, you want all the help you can get. But these medications do have their side effects.
For example, some pain medications, like NSAIDs, can cause dysbiosis if they’re used too often. This would then compromise your gut wall’s integrity, causing the tight junctions in that wall to separate more. These leaks would allow substances into your bloodstream that shouldn’t be there, prompting a GALT response and inflammation. And, because these leaks are there, especially if you keep taking NSAIDs, that cycle keeps repeating. The chronic inflammation then spreads throughout the body, including to your brain and nervous system. That can potentially make your migraines worse over time and even create other neurological and psychiatric problems down the line.
Other drugs used for migraines, like triptans, can increase your risk of strokes or heart attacks if you’re already at risk. Dihydroergotamine, like Migranal, can worsen your nausea and other migraine-related GI symptoms. Ubrogepant can cause dry mouth, nausea, and dizziness. You should avoid opioid medications when possible because they can be highly addictive.
There are other medications not listed here, but all of them have side effects and increase your risk for other issues, especially if you have to take them often. This is why it’s important to give vagus nerve stimulation serious consideration.
Vagus nerve stimulation inhibits something called cortical spreading depression, or CSD. CSD is a kind of wave of neuronal depolarization that spreads throughout the brain. Depolarization is basically deactivation. Neurons can either depolarize/deactivate, or repolarize/activate, depending on the electrical and chemical signals they’re receiving and transmitting.
CSD has been associated with migraine auras, as well as seizures and brain ischemia. Migraines can come in three possible phases: aura, attack, and post-drome. Most people experience just the attack, but some can experience all three.
Aura symptoms include weakness in the muscles and limbs, involuntary movements, visual and auditory disturbances, and difficulty speaking. The attack encompasses the pain and full symptoms of the migraine. And post-drome is when you feel a bit dizzy, weak, sensitive, and irritable once the attack is over.
CSD induces neuroinflammation. It increases the levels of the inflammatory cytokines IL-1β and TNF. Neuroinflammation activates your microglia and puts your neurons in a defensive state, which makes it difficult for them to repair and restore any damage. Neuroinflammation is also a big factor in many pain conditions, including fibromyalgia, as well as neurodegeneration and mental health issues.
Vagus nerve stimulation can help lower the level of CSD-triggered cytokines, thereby lowering the level of inflammation in the body. But it is definitely not something that can replace a healthy diet and lifestyle changes; it should only be used to complement them.
If you’d like to learn more about our holistic approach to lowering inflammation as well as how we help our clients deal with migraines and other pain conditions, you can get in touch with us for a free initial consultation. We also offer functional tests that can help determine any nutrient deficiencies, food sensitivities, and other important information.
PTSD is a challenging condition that often comes with memory flashbacks, anxiety, insomnia, hypervigilance, and depression. Non-invasive vagus nerve stimulation studies for PTSD show some hopeful possibilities.
In one study, participants had a 46% decrease in their autonomic anxiety scores. Another showed a 31% improvement in the PTSD checklist scores, which is a measure of all DSM-5 symptoms. And, in another study, vagus nerve stimulation decreased IL-6 levels, which is another inflammatory cytokine, and one which increases from traumatic stress.
These results, along with the results of other studies, show that not only can vagus nerve stimulation reduce symptoms, but it can also address the neurobiological basis of PTSD and PTSD triggers. And it seems to do that through the noradrenergic and peripheral sympathetic nervous system.
Non-invasive vagus nerve stimulation is emerging to be one of the more promising approaches to dealing with certain challenging conditions. It seems to help with migraines and other pain conditions, reparatory difficulties, and PTSD. Other studies showed its potential for alleviating Parkinson’s Disease symptoms and respiratory difficulties.
Indirectly, it may also reduce the reliance on opioids for pain relief and thereby aid in the fight against the opioid crisis.
It works through four main mechanisms of action. Vagus nerve stimulation:
Non-invasive vagus nerve stimulation is a safe, effective, and potentially sustainable therapy option for many conditions. But it's important to remember that it is not a magic bullet. In our experience, which spans decades as well as thousands of patients, there is no one type of therapy that can replace holistic recovery plans. Diet and lifestyle changes are a must, especially for those with chronic conditions and adrenal fatigue.
If you’d like to learn more about our nutritional coaching plans and functional testing, we’d be happy to discuss those with you in a free initial consultation. We’ve worked with patients with a variety of conditions, including all of the ones discussed in this article.
Vagus nerve stimulation has been around a while, but now instead of implanting a device in your neck, you can use a non-invasive device. It can help with migraines, respiratory difficulties, PTSD, chronic inflammation, and even Parkinson’s Disease symptoms. But it doesn’t replace diet and lifestyle changes.