Medical experts have been studying the relationship between the brain and the gut for years, particularly how psychological stress can impact gut health, including its impact on microbiome diversity and digestion. Toby Melville/Reuters

According to a recent study from the Perelman School of Medicine at the University of Pennsylvania, cells that are involved in communication between psychological stress responses in the brain and inflammation in the gastrointestinal (GI) tract have been identified in animal models.

These cells, specifically glial cells, support neurons and communicate stress signals from the central nervous system and travel to the nervous system within the GI tract, known as the enteric nervous system, subsequently causing inflammation within the bowels.

Today, it is estimated that over 1.5 million Americans currently suffer from inflammatory bowel disease (IBD), which covers Crohn's disease and ulcerative colitis; both of which can spark symptoms ranging from frequent diarrhoea, abdominal pain and blood in the stool, whilst persistent inflammation of the bowels can eventually lead to permanent damage within the GI tract. Current treatments consist of anti-inflammatory medication, steroids and changes to your diet.

Christoph Thaiss, PhD, assistant professor of Microbiology and senior author of the study, commented on the nature of the study, saying: "Clinicians have long observed that chronic stress can worsen IBD symptoms, but until now, no biological connection has been identified to explain how the digestive system knows when someone is stressed."

The researchers used mice with IBD to conduct their experiments and the team discovered, as is customary with humans, that the mice developed severe symptoms when they experienced stress. Researchers traced the initial stress response signals to the adrenal cortex that, in turn, released glucocorticoids, which are steroid hormones known for activating psychological responses to stress throughout the body.

Ostensibly, the neurons and glial cells within the ENS responded to chronically-elevated levels of glucocorticoids, suggesting a significant link between precepted stress in the brain and inflammation of the intestines.

While it is typical for glucocorticoids to have an anti-inflammatory effect on the body, the researchers found that when the glial cells within the ENS were exposed to the hormones for an elongated amount of time and during periods of chronic stress, they attracted white blood cells to the GI tract, thus increasing the inflammation. Also, when exposed to chronic stress, the neurons in the ENS and GI tract ceased their natural function, which can potentially lead to impaired bowel movements and exacerbated IBD symptoms.

Senior members of the study examined the results, and verified the connection between psychological stress and IBD symptoms in humans by using the UK Biobank, a large-scale biomedical database, along with a cohort from the IBD Immunology Initiative at Penn Medicine. They later discovered that, in patients diagnosed with IBD, the level of reported stress correlated with increased severity of IBD symptoms.

Maayan Levy, PhD, fellow assistant professor of Microbiology and co-senior author of the study, spoke of the results: "This finding highlights the importance of psychological evaluations in patients being treated for IBD, as well as to inform treatment protocols. One of the most common treatments for IBD flare-ups is steroids, and our research indicates that in patients with IBD who experience chronic stress, the efficiency of this treatment could be impaired."

The researchers underlined their study by insisting on opportunities for further research into the biology of glial cells along with the various roles they play in systems throughout the body, including communication between the nervous and immune systems.