Vagus Nerve as Modulator of the Brain–Gut Axis in Psychiatric and Inflammatory Disorders

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.

Short but Continuous Natural Pain during Meditation Sittings for Depression Treatment: A Case Report

“…In this sense, SCP lasts long enough to trigger significant changes in the pain pathways and potentially benefit depression recovery despite shifting maladaptative states of the body, through fine tuning the interconnected endocrine, immune, and nervous systems. Similarly, exercise, fish oil consumption, controlled breathing, and other relaxation therapies have been implicated in increasing vagus nerve activity and decreasing pro-inflammatory cytokine release, consistent with observed clinic benefits of vagus nerve stimulation against depression (9,(32)(33)(34). Last but not least, Meditation associated pain has also been described by others (35).…”

Genome-wide association study of gastrointestinal disorders reinforces the link between the digestive tract and the nervous system

“…22 Figure 3B shows the rg between each of the six phenotypes and selected traits from the 258 traits. 23 Interestingly, we observed significant rg between three digestion phenotypes and depressive symptoms 38 24 (GORD (0.46, SE = 0.05, PH0:rg=0 = 1.7E-21), PUD (0.52, SE = 0.09, PH0:rg=0 = 1.2E-9), IBS (0.52, SE = 0.07, PH0:rg=0 = 25 1.5E-12)). IBS was significantly genetically correlated with major depression (MD) 39 (0.43, SE = 0.10, PH0:rg=0 = 26 2.1E-5)).…”

“…As discussed by Finucane et al 41 , it is not possible to draw 13 strong conclusions about the most likely causal tissue or cell type as only a subset of cell types are tested, we 14 can only say tissues with similar gene expression profiles to BA9 of brain or BA9 itself may be relevant to 15 GP+M. Given the non-availability of gene expression data from other human tissues, such as sympathetic, 16 parasympathetic (vagus nerve) 23 and enteric nervous system 22,24 , we cannot conduct key hypothesis based 17 enrichment analyses. However, despite these limitations, our findings indicate that a genetic contribution to 18 GP+M may highlight the potential link between the nervous system and oesophagus, stomach and duodenum 19 though there is likely not just one causal tissue or cell type.…”

MicroCT optimisation for imaging fascicular anatomy in peripheral nerves

“…Determining this in the ANS has recently become relevant because of the development of Electroceuticals, treatment of endocrine, autoimmune and other diseases by electrical stimulation of autonomic nerves (Bonaz et al, 2018;Breit et al, 2018;Browning et al, 2017;Koopman et al, 2016). At present, this is achieved by electrical stimulation of the entirety of the nerve.…”