How Do Chronic and Acute Stress Affect the Gastrointestinal Tract?

Disrupted Communication

Stress-induced changes in the GI tract may increase vulnerability to various digestive disorders. Disruption of gut-brain axis communication can manifest in multiple ways, underscoring the need to better understand mechanisms involving the enteric nervous system, visceral sensitivity, intestinal barrier function, and gut microbiota.

Gastroenterology and psychiatry could both benefit from the integration of these insights.

Effects on the Enteric Nervous System

The enteric nervous system plays a crucial role in GI function. Activation of stress hormones significantly affects its performance. Increased sympathetic activity, a hallmark of the acute stress response, leads to the release of noradrenaline in various parts of the body, including the GI tract.

Immunohistochemical data show that noradrenaline, for instance, can suppress intestinal motility. However, questions remain about how stress influences the production of corticotropin-releasing hormone (CRH).

Increased Visceral Pain

One common outcome of stress on the GI system—regardless of stress type—is heightened visceral pain. Studies examining acute stress and visceral sensitivity found that mental stress induced by dichotomous listening tests increases pain in the sigmoid colon, but not in the transverse colon.

More recent findings suggest that this heightened sensitivity occurs only in individuals with irritable bowel syndrome (IBS), pointing to the potential role of pre-existing functional changes in the gut.

Another study found that a brief anxiety-inducing task did not cause changes or discomfort in the distal colon, suggesting variability in how different parts of the GI tract respond to stress.

Impact of Stressors on the Intestinal Barrier

Clinical studies suggest that acute stress may increase the permeability of both the small and large intestine. In healthy individuals, this occurs via paracellular—not transcellular—pathways. Stress also boosts immune cell activity in the rectal mucosa.

However, not all stressors provoke the same response. For example, a 2021 Swedish study on healthy individuals undergoing tandem skydiving showed no increase in intestinal permeability from this type of stress.

Another study investigating public speaking as a stressor found that increased small intestine permeability occurred only in individuals with significantly elevated cortisol levels.

A Spanish study added that acute stress had a greater effect on gut permeability in people already experiencing mild, chronic stress compared to those with low overall stress exposure.

The Role of the Microbiome in Stress Response

The gut microbiome is essential for proper GI functioning—not only in maintaining intestinal integrity and immunity, but also in supporting nutrient absorption and infection protection. Current evidence also highlights its key role in maintaining signaling within the hypothalamic-pituitary-adrenal (HPA) axis and the sympatho-adrenal-medullary system.

According to a Dutch study on probiotics and neurocognitive functions, altering the gut microbiota with probiotics can improve both physiological and subjective stress responses. In contrast, Belgian researchers found no such effect with prebiotics.

Direct effects of acute stress on microbiota composition and function remain understudied. However, *in vitro* research suggests that gut microbes may interact with stress hormones and produce a range of neuroactive compounds.

What Has Been Proven?

The Irish and American authors of the review conclude that stress clearly affects gastrointestinal function. Chronic stress has long-term consequences for the gut-brain axis, is linked to dysregulation of the enteric nervous system, and disrupts intestinal motility. It also increases visceral sensitivity and affects intestinal barrier function.

Available findings show that acute stress may influence gut permeability, impact immune cell populations, and alter serotonin levels in the GI tract.

However, the authors emphasize the need for further research to better understand the complex interactions between acute and chronic stress and their effects on different GI responses. These insights could ultimately enhance diagnostic and therapeutic options in both gastroenterology and psychiatry.

Editorial Team, Medscope.pro

Source: Leigh S. J., Uhlig F., Wilmes L. et al. The impact of acute and chronic stress on gastrointestinal physiology and function: a microbiota-gut-brain axis perspective. J Physiol 2023 Oct; 601 (20): 4491–4538, doi: 10.1113/JP281951.