What Happens in Vagus: Chronic Pain and Dysautonomia

I’ve been doing a lot of reading lately about the vagus nerve and the autonomic nervous system. We’ve been super fortunate to work with a handful of patients with POTS in the past 6 months with some really great and surprising results from taking a cervical and vestibular approach to care, and it’s driven me to learn more about this unconscious super system in the body.

While dysautonomia is considered a rare problem, there are actually certain types of patients that have a higher risk of having dysautonomia as a co-morbid condition. This includes neurodegenerative disorders like multiple sclerosis and Parkinson’s Disease, but the ground I want to cover is something that affects people as an invisible illness.

Today we’re going to breakdown the relationship between chronic pain and the vagus nerve.

Fibromyalgia, Chronic Fatigue, and Dysautonomia

Fibromyalgia and chronic fatigue syndrome (aka myalgic encephalomyelitis) are 2 conditions that are frequently associated with each other. Estimates as high as 75% of of fibromyalgia patients report fatigue as a major symptom and 20% of chronic fatigue patients also report having widespread body pain [source].

What’s unique about these disorders is that they both show an unusually high amount of dysautonomia compared to the general population. A review in the Journal of Clinical Rheumatology showed that patients with fibromyalgia frequently show scores reflecting autonomic dysfunction along with non-pain symptoms like light-headedness on standing (orthostatic intolerance), digestive complaints, excess sweating, and fatigue.

It’s also been reported in the Journal of Internal Medicine that patients with chronic fatigue syndrome frequently have postural orthostatic tachycardia syndrome (POTS) enough to classify the POTS patients as a distinct subgroup of chronic fatigue.

So why is chronic pain associated with this breakdown of the autonomic nervous system?

What Happens in Vagus….

The nervous system is classified into different branches. For ease of understanding, you have one branch that controls all of your muscles like your biceps, triceps, and quads called the somatic nervous system. You also have another branch that controls your organ systems called the autonomic nervous system.

The autonomic nervous system is further divided into the sympathetic nervous system and the parasympathetic nervous system. The sympathetic system is the one that causes the things you feel when you get stressed out. Rapid heart beat, sweating, high blood pressure, along with increased blood flow to your muscles. It helps you prepare to fight or escape danger. The sympathetic system is primarily driven by a bundle of nerves called the sympathetic chain.

The parasympathetic does the opposite. It forces you to breathe slowly, digest, breathe slowly, and think about reproducing. The parasympathetic system is mainly driven by your vagus nerve.

The Vagus Nerve has a direct connection to most of your body’s internal organ systems

These systems generally work in opposition to each other to set the tone for how your body is going to operate.

The vagus nerve is an special and unique nerve that travels from your brainstem into the bulk of your internal organ systems. It gives the brain a direct line of communication with your organ systems because your body generally wants to spend most of it’s time being parasympathetic. 


Because when your body is more parasympathetic it is able to breath easier, digest better, engage in sexual intercourse, sleep, and heal from injury.

The sympathetic system is designed to help you survive from an imminent threat, but your parasympathetic system is there to ensure that you can adequately heal and recover from that threat.

The more active the Vagus nerve is, the more likely your body is able to heal and recover. This isn’t just some pleasant billboard sticker either. Research has shown that increased parasympathetic activity is associated with higher survival heart disease and cancer. It’s also associated with improved recovery and decreased injury in athletes.

Most importantly for the patient in chronic pain, lower vagus nerve activity was associated with chronic pain compared to healthy controls. [Source] It’s also been shown that lower vagus activity can be associated with intensity of symptoms in patients with fibromyalgia. [Source]

Weak Vagus and Chronic Stress

Vagal activity is measured using something called heart rate variability (HRV). Many years ago, you could only measure heart rate variability from electrocardiograms (EKG) and measuring the distance between each heart beat. Today, there is no shortage of computer and even smart phone applications that have brought HRV to a wide audience.

In general terms, the higher your HRV is over time, the higher your vagal or parasympathetic activity. The lower your HRV is over time, the higher your stress or sympathetic activity.

If your body is in a chronically high state of stress, then it is going to:

  • Decrease blood flow to your organs
  • Increase exposure to your stress hormones (adrenaline and noradrenaline)
  • Decrease your stores of serotonin (feel good neurotransmitter)
  • Increase your blood sugar (diabetes)
  • Increase your blood pressure
  • Decrease your immune system
  • Decrease tissue healing

Why? Because if your brain thinks that it is in danger from attack, then it does not care about healing and immune function. It is strictly concerned about getting you out of danger.

When you have low HRV and high sympathetic activity, your body is at a distinct disadvantage when it comes to healing and resilience. While low HRV isn’t necessarily the cause of heart disease, cancer, fibromyalgia, or chronic fatigue, but if you have a low HRV then your body’s ability to adapt and overcome these conditions is compromised.

I’ll put that in bold text because that’s an important distinction:

When you have low HRV and high sympathetic activity, your body is at a distinct disadvantage when it comes to healing and resilience. While low HRV isn’t necessarily the cause of heart disease, cancer, fibromyalgia, or chronic fatigue, but if you have a low HRV then your body’s ability to adapt and overcome these conditions is compromised.

Bringing Vagus Back

There was an interesting study published in 2014 that used strength exercise as a treatment for patients with fibromyalgia. The study showed that patients with Fibromyalgia had significant improvements in pain and quality of life through a regiment of strength training, but no significant changes in HRV. The study was surprising, because exercise is one of the best, easiest, and cheapest ways you can improve your HRV, but the biggest surprise was in the conclusion. The study concluded that strength training was an effective therapy for patients with fibromyalgia, which is absolutely true, but also said that changing the autonomic nervous system is not a goal worth achieving in patients with fibromyalgia.

Knowing what you know now about the autonomic nervous system, it seems like a rational and reasonable goal for any patient because improving the autonomic nervous system improves the health and survival of patients regardless of what condition they have.

The best part is that vagal tone can be improved using non-invasive methods that include cardiovascular exercise, resistance exercise, breathing exercise, mindfulness training, non-invasive vagal nerve stimulation, and yes even upper cervical chiropractic.

By taking the focus away from just addressing the pain, and making the focus of care on the autonomic nervous system, it gives us the ability to affect the person as a whole, instead of just addressing a symptom. By taking people away from their condition, and returning them to their bodies.


Ask Dr. Chung a Question

Post Traumatic Stress Disorder, Heart Rate Variability, and Brain Resiliance



Read Time: [6 min]

“The brave men and women, who serve their country and as a result, live constantly with the war inside them, exist in a world of chaos. But the turmoil they experience isn’t who they are; the PTSD invades their minds and bodies.”  – Robert Koger

“You can’t patch a wounded soul with a Band-Aid.” –  Michael Connelly

“Always remember, if you have been diagnosed with PTSD, it is not a sign of weakness; rather, it is proof of your strength, because you have survived!” –  Michel Templet

One of the important things about an election years is that it brings light to topics that rarely see the light of day under normal circumstances. That happened this week as Donald Trump spoke about the need for more mental health resources to help veterans afflicted with PTSD.

“When you talk about the mental health problems, when people come back from war and combat, and they see things that maybe a lot of the folks in this room have seen many times over – and you’re strong and you can handle it – but a lot of people can’t handle it,”

The quote ended up getting taken WAY out of context over the past few days with media outlets saying that “Donald Trump calls soldiers with PTSD weak”. Trump says a lot of things that are polarizing, but I don’t think this was said with an inflammatory intent. It does however highlight the power that words have when discussing health conditions.

Here is the part that I care about: Is PTSD just a matter of mental toughness, or is there something happening physiologically where we can intervene and help make the brain more resilient?

What Happens in the Brain in People with PTSD?

PTSD is a diagnosis with strict criteria, but it’s mainly classified by a patient who routinely relives a traumatic event to the point where it disrupts their normal behavior. This could mean that you have flashbacks, nightmares, or hallucinations from the traumatic episodes. This reliving of an event can lead to avoidance, erratic behavior, depression, and anxiety.

Historically, PTSD has been considered a psychological disorder and despite the mounting evidence to the contrary, psychological disorders carry a stigma of being weak minded.

In more recent years, scientists have been able to identify some real changes in the physical and functional features of the brain. Here’s what we know so far.

  • Shrinkage….of the Hippocampus – MRI studies of patients with PTSD compared to control showed that the memory storing region of the brain is physically smaller. Previous studies have shown that high exposure to the stress hormone cortisol can injure brain cells in the hippocampus.Loss of hippocampal function affects your ability to differentiate between memories and present time events.
  • Hyperactive Amygdala – the amygdala is the seat of emotions in the brain. It is particularly active with intense feelings like fear and sadness. Patients with PTSD have been shown to have increased blood flow to this particular part of the brain
  • Cutting the Breaks – the ventromedial prefrontal cortex is a part of the brain that acts as the CEO of the brain’s emotional response. It serves as the break system to make sure that parts of the brain like the amygdala don’t dominate our experience with purely emotional behavior. In PTSD this part of the brain loses some of the capacity to control the amygdala which allows the Amygdala to become hyperactive.

Heart Rate Variability and the Resilient Body

I love talking about resiliency.

It represents our ability to meet a challenge, survive it, and come out stronger than before.

I’ve always seen the body as a resilient structure. When you are in constant pain or always sick, it’s easy to forget that our bodies are exposed to an insane amount of stress, but it still finds a way to keep us above ground.

One of the most sought after metrics to measure resiliency is a test called Heart Rate Variability or HRV for short. By measuring small differences in the rhythm of your heart beat, HRV gives us an idea of how well your brain controls your organ systems like your heart and intestines.

But that stuff isn’t really that important for your purposes. What you need to know about HRV is that it is an excellent predictor for how resilient your body is to stress and illness.


People with high HRV predict better survival rates for things that put you in imminent danger like cancer, heart attack, and stroke. It can also predict your response to stress, inflammatory response, empathy, and even your recovery from training.

If I had to pick one way to describe HRV, it’s that it is the measurement helps to determine how well your body is going to heal or bounce back.

 PTSD, HRV, and the Brain

We’ve known for a long time and in a lot of studies that people with PTSD have lower HRV. However, we didn’t know if people with lower HRV led to PTSD or if someone getting PTSD led to a lower HRV.

A 2015 study in the prestigious journal JAMA Psychiatry looked to provide some evidence. They studied over 2,000 marines getting deployed into combat. All of the marines had their HRV measured before deployment, and when the marines returned home they were evaluated for PTSD.

The study showed that soldiers with lower HRV had a significantly higher risk of developing PTSD

Now here’s where things get interesting. Remember that part of the brain that acts like the brakes on the brain’s emotional response in PTSD? It’s called the ventromedial prefrontal cortex. As it turns out, this part of the brain is also a big part in the regulation of HRV!

In a 2011 study in the journal Neuroscience and Behavioral Reviews, the authors looked at brain imaging studies and found that HRV is tied to blood flow in the brain in that very same area. When that part of the brain is activated, people have a stronger ability to remain calm and control their emotional responses to stress.

When you have better control over your stress response, you gain control over the health of your body.

Best of All, HRV is Under Your Control

We think about someone’s health and their risk of getting disease, we often associate it to bad luck and bad genes.

The beautiful thing about HRV is that we can readily change our HRV. Things like meditation sleep, biofeedback, exercise, and even chiropractic can stimulate the right part of our brains that can improve our HRV! The reason these things seem to have such an big role in stress management might be because they improve blood flow and activation to the brakes in our brains.

How does the spine affect HRV?

How does the spine affect HRV?


In fact, we have been working with some patients on programming ways for people to improve their HRV and seeing how this improves their performance in exercise and overall health. The results so far have been promising.

Now it’s still way too early to say that we should put all of our eggs in the HRV basket. Most studies have identified correlation, and causation is still up in the air. But if we can reliably measure stress using HRV and use these inexpensive, safe, and simple ways to improve your brain’s response to stress, then there’s greater chance that we can help these soldiers start to kick out of the suffering of PTSD.

Talk to Dr. Chung about HRV


Research: Active Vagus Nerve Predicts Cancer Survival Regardless of Stage

The Vagus Nerve and Cancer


  • What’s a Vagus nerve?
  • Sympathetic vs Parasympathetic
  • The Startling stats on HRV and Tumor Blood markers
  • How You Can Improve Your Vagus Nerve Activity
  • Tools to use today

Abstract Link:

If you have an active vagus nerve, cancer stage may no longer be important

I don’t usually like to post articles about cancer because it’s a sensitive subject that affects a lot of people. I just had to write about this because it’s really fascinating and really surprising. I’ll be interested in seeing how research in this field evolves. So here we go.

Active Vagus Nerve? What’s That?

The vagus nerve is probably the most interesting nerve in the body. It goes from your brainstem and connects to almost every organ in your body that you hardly think about. Check it out below:

Vagus Nerve

Historically, this nerve is associated with creating a parasympathetic response for the body. A parasympathetic response is essentially the opposite of a sympathetic (aka stress response).


Fight or flight

Speed Up Heart Rate

Slows down digestion

Down Regulate Immune System


Feed and Breed

Slows down heart rate

Turns up digestion

Up Regulate Immune System

We need both of these systems working properly in order to be healthy. Our sympathetic system helps us to run away from danger and perform outrageous feats of athleticism when activated properly. Our parasympathetic system helps us to prepare for sleep and improve digestion and absorbtion of vital nutrients.

Life is really about finding a balance between these subsystems of your nervous system. It’s extremely common in our stressed out world to be sympathetic dominant. This dominance is what leads many people to have problems like high blood pressure, irritable bowel syndrome, diabetes, and other chronic illness.

While we cannot always control the environment that causes us to be stressed out, there are things we can do in our daily lives to help activate our vagus nerve and turn on our parasympathetic nervous system.

The Vagus Nerve and Cancer

So that’s all well and good, but how does that line up with something as deadly as cancer?

The authors used a metric called Heart Rate Variability(HRV) to monitor activity of the vagus nerve. Heart Rate Variability monitors the rhythm changes between consecutive heart beats and is highly correlated to the activity of the vagus nerve.

In previous studies, high HRV scores have been associated with lower tumor burden and increased survival in cancer patients. [1,2,3] but it wasn’t known whether high vagal activity was the cause of improvement or just a characteristic of people that recover well.

Here’s what the authors of this study found:

Patients with prostate cancer and colorectal cancer were studied. The stage of cancer and heart rate variability were measured before treatment to see if they predicted tumor markers at a 6 month follow up.

Image from Paper:

Prostate Cancer markers and HRV Image from copy of paper:

Image from paper:

Colorectral Cancer markers and HRV Image from paper copy:

 These graphs were the most eye opening part of the paper. Each graph shows the presence of cancer biomarkers. For prostate cancer they used Prostate Specific Antigen (PSA). For colorectal cancer they used CarcinoEmbryonic Antigen (CEA).

These graphs show that patients with high vagal nerve activity (high HRV) had substantially lower levels of tumor markers in their system compared to patients with low vagal nerve activity (low HRV) in late stage cancer. This was true even when accounting for age and treatment differences. What does this mean?

If you have metastatic or late stage cancer, having higher vagal activity can reduce your tumor burden and improve your odds at recovery.

Can I Improve my Vagus Nerve Activity?

So can you actually improve your vagus nerve activity, or is it something that you’re born with? As it turns out, there are not shortage of things that you can do to help improve your heart rate variability. These interventions include:

Regular activity and exercise
Diet and Gut Bacteria Changes
Meditation, Stress Management, Biofeedback
Massage (Even in Infants)

And that was just from a quick search on Pubmed.

The point being:

Heart rate variability/vagal activity is something you can change whenever you want.

Not a Cancer Treatment

Now here’s where things get sticky and why I don’t post about cancer in my blog. In the alternative medicine world, it’s easy for some people to take the results of one study, and extrapolate in a way to say that makes it out to be the big thing to cure cancer naturally.

 Changing your vagal tone and HRV is NOT about treating cancer, and anyone using the above methods as a stand alone methodology of curing cancer is foolish.

Getting better function from your vagus nerve is about creating higher resilience in your body’s response to stress isn’t just good for cancer. It’s good for just about everything from post-exercise recovery to post-heart attack recovery.

Regardless of your condition, a better adaptation to stress benefits the body as a whole.

Tools for You

Heart Rate Variability is one of the metrics that we measure on patients in our office. It helps us keep a gauge of a patient’s autonomic nervous system in response to a Structural Correction program.

Fortunately, technology has evolved to the point where you can actually measure this on yourself regularly right from your own phone. While I have never used these apps before, these tools can provide a motivated patient to take their own measurements comfortably from their own home. Here are the highest rated tools:

Polar H7 Blue Tooth Smart Heart Rate Monitor (Starting at $55)

Elite HRV App (Free)

I suggest taking measurements over the course of a few days to get some baseline data before you start seeing what creates positive change. It’s important to control for certain variables. I would start by taking your HRV the first the in the morning so it helps eliminates some confounding variables. Remember that HRV can be influenced by numerous factors including sleep, prescription drugs, diet, and timing of the test.. It’s up to you to find the right combination that works for you.

Use these measurements to time your post-workout recovery, physiologic response to new treatments, or even the impact that sleep has on our overall health. While it’s not a full-proof measurement by any means, it’s a non-invasive and significant marker for overall health and well-being.