Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders
Kristen Sparrow • March 18, 2023
I’ve been alerted to ever more mention of the vagus nerve in the popular press. I’ve been interested in the vagus nerve and parasympathetic activity for longer than I choose to admit. That is why I measure Heart Rate Variability in the clinic to get a glimpse into patients’ parasympathetic tone overall and how it reacts to treatment. Patients might also be receiving TAVNS, or transcutaneous vagal nerve stimulation with their treatments. This is a noninvasive way of stimulation the autonomic nervous system, though it’s still under study. Acupuncture also stimulates parasympathetic activity! I only use TAVNS in conjunction with acupuncture, but some of my patients use TAVNS at home also with a device I’ve fashioned for them.
I would add to the summary of the study below, that depression and other mood disorders are probably attributable, in part, to inflammation. And improving vagal activity has been shown to lower inflammation throughout the body. The chemical imbalance theory of depression has never been convincingly proven.
Breit S, Kupferberg A, Rogler G, Hasler G. Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders. Front Psychiatry. 2018 Mar 13;9:44. doi: 10.3389/fpsyt.2018.00044. PMID: 29593576; PMCID: PMC5859128.
Abstract
The vagus nerve represents the main component of the parasympathetic nervous system, which oversees a vast array of crucial bodily functions, including control of mood, immune response, digestion, and heart rate. It establishes one of the connections between the brain and the gastrointestinal tract and sends information about the state of the inner organs to the brain via afferent fibers. In this review article, we discuss various functions of the vagus nerve which make it an attractive target in treating psychiatric and gastrointestinal disorders. There is preliminary evidence that vagus nerve stimulation is a promising add-on treatment for treatment-refractory depression, posttraumatic stress disorder, and inflammatory bowel disease. Treatments that target the vagus nerve increase the vagal tone and inhibit cytokine production. Both are important mechanism of resiliency. The stimulation of vagal afferent fibers in the gut influences monoaminergic brain systems in the brain stem that play crucial roles in major psychiatric conditions, such as mood and anxiety disorders. In line, there is preliminary evidence for gut bacteria to have beneficial effect on mood and anxiety, partly by affecting the activity of the vagus nerve. Since, the vagal tone is correlated with capacity to regulate stress responses and can be influenced by breathing, its increase through meditation and yoga likely contribute to resilience and the mitigation of mood and anxiety symptoms.
