The Vagus Nerve Explained.
What is the Vagus Nerve?
The vagus nerve is the longest nerve in the body - vagus means "to wander" in Latin. Originating in the medulla of the brainstem, it travels down the neck, touching the heart and lungs, snaking all around the digestive system to the lowest viscera of the abdomen, interacting with most major organs - like the liver, spleen and pancreas - along the way. This nerve controls all involuntary bodily processes and is a major player in the activation of the parasympathetic nervous system, which is responsible for our ‘rest and digest’ state (the opposite to the sympathetic nervous system, which is the operator of the ‘fight or flight’ state).
The vagus nerve is one of the most important conduits of the mind-body connection. It is the central command for bidirectional communication between the two, allowing the mind to influence the body and the body to influence the mind.
The management and processing of emotions happen via the vagus nerve, it is what registers the physical and mental sensations of heartbreak or gut-wrenching feelings. It is the mechanism through which a person can perceive that they feel angry or upset and then notice that their throat is dry, their voice is tense, their heart is thumping and their breathing is rapid and shallow.
What is Vagal Tone?
As I mentioned the vagus nerve controls our involuntary bodily processes, everything from heart rate, blood pressure, digestion and gut function to orgasms and fertility. A healthy vagus nerve optimises all of these systems, as well as allowing us improved access to the parts of the brain responsible for creativity, leadership, emotional regulation, higher cognition and complex decision making. Higher vagal tone means a healthier nervous system, and the healthier the nervous system the faster you can change gears, meaning your body can relax rapidly after a flood of stress.
You can measure your vagal tone by measuring your heart-rate variability (HRV). High HRV is an indicator of high vagal tone. A consistent yoga, meditation* and/or exercise routine have been proven to significantly increase HRV and vagal tone.
*Particularly Metta (or loving-kindness) meditation. There is a surprising amount of science suggesting that increasing our positive thoughts towards others leads to an improvement in vagal function as seen in heart-rate variability.
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Higher vagal tone is also associated with better mood, less anxiety and more stress resilience. One of the most interesting roles of the vagus nerve is that it essentially reads the gut microbiome and initiates a response to modulate inflammation based on whether or not it detects pathogenic versus non-pathogenic organisms. In this way, the gut microbiome can affect your mood, stress levels and overall inflammation via the vagus nerve - which brings us back to that mind-body connection.
What is Low Vagal Tone Associated With?
Low vagal tone is associated with cardiovascular conditions and strokes, depression, diabetes, infertility, chronic fatigue syndrome, cognitive impairment, and much higher rates of inflammatory conditions. Inflammatory conditions include all autoimmune diseases like rheumatoid arthritis, inflammatory bowel disease, celiac disease, endometriosis, autoimmune thyroid conditions, lupus and more.
The functioning of the vagus nerve can be impaired in the short and longterm by psychological stress and anxiety, poor lifestyle choices like smoking, drinking, mental and/or physical overexertion, lack of exercise, poor quality nutrition and sleep.
How to Increase Vagal Tone?
The increasing of vagal tone through neuromodulation is emerging as an exciting new therapeutic field in psychiatric treatment. Doctors have started stimulating the vagus nerve with electrical impulses from a small device implanted into the body, adopting a bottom-up approach to modulating the neural circuitry of depression by stimulating vagal activity. This approach is being successfully used to treat acute cases of severe depression which often failed to benefit from first-line approaches like clinical intervention and pharmaceuticals.
I hope this demonstrates just how powerful good vagal tone is for our mental health and overall wellbeing, and why it would be a worthwhile investment to dedicate a little time to tend to it daily. The good news is we can access all the benefits of good vagal tone ourselves with just a little simple knowledge and a commitment to regular practice. To some degree, we are all genetically predisposed to varying levels of vagal tone, but this still doesn’t mean that we can’t change it.
In addition to (or even in the absence of) a consistent yoga, meditation and/or exercise routine, here are the surprisingly simple ways we can tone the vagus nerve:
How to Know You’ve Activated the Vagus Nerve?
Simple, your tear ducts will activate or your eyes will water. The extent to which this occurs is the extent to which you’ve activated the vagus nerve with the use of these techniques. I always get the best activation from the Wim Hof Method breathing technique.
Dr Stephen Porges pioneered this theory and it is one of the most important recent developments in human neurobiology. If you would like to learn more on the topic, I highly recommend this book. It is a quick, fascinating and practical read that builds on Porges’s theory, summarising over 30 years of experience and knowledge in the area.
References
Davis, M., Eshelman, E. R. & McKay, M. (2008). The relaxation & stress reduction workbook. (6th ed.). New Harbinger Publications: CA, USA.
Gerritsen, R. J. S. & Guido, P. H. B. (2018). “Breath of Life: The Respiratory Vagal Stimulation Model of Contemplative Activity.” Frontiers in Human Neuroscience, Frontiers Media S.A. Retrieved from www.ncbi.nlm.nih.gov/pmc/articles/PMC6189422/.
Kok, B. E., et al. (2013). “How Positive Emotions Build Physical Health: Perceived Positive Social Connections Account for the Upward Spiral between Positive Emotions and Vagal Tone.” Psychological Science, U.S. National Library of Medicine. Retrieved from www.ncbi.nlm.nih.gov/pubmed/23649562.
O'Reardon, J. P., et al. (2006). “Vagus Nerve Stimulation (VNS) and Treatment of Depression: To the Brainstem and Beyond.” Psychiatry (Edgmont (Pa. : Township)), Matrix Medical Communications. Retrieved from www.ncbi.nlm.nih.gov/pmc/articles/PMC2990624/.
Porges, S. W. (2014). The Pocket Guide to The Polyvagal Theory: The Transformative Power of Feeling Safe. WW Norton & Co: NY, US.
Rosenberg, S. (2018). Accessing the Healing Power of the Vagus Nerve : Self-Help Exercises for Anxiety, Depression, Trauma, and Autism. North Atlantic Books: US.
Van Der Kolk, B. (2014). The body keeps the score: Mind, brain and body in the transformation of trauma. Penguin: UK.
Yang, J. & Ji Hoon, P. (2019). “The Present and Future of Vagus Nerve Stimulation.” Journal of Korean Neurosurgical Society, Korean Neurosurgical Society. Retrieved from www.ncbi.nlm.nih.gov/pmc/articles/PMC6514309/.