Psychological stress can exacerbate certain digestive tract inflammations caused by intestinal diseases. Now, American scientists have identified the reason for this. The relevant paper was published in Cell on May 25th. The new study provides a comprehensive narrative - from the chemical signals generated by the brain to the immune cells in the intestines, which brings trouble to people with these diseases. This study helps to explain how chronic stress causes physical pain, indicating that controlling stress levels may have a profound impact on the treatment effectiveness of inflammatory bowel disease (IBD). The author of the paper and microbiologist Christoph Thaiss from the University of Pennsylvania in the United States stated that this idea runs counter to traditional medical methods, which "completely ignore the patient's psychological state as the main driving factor of treatment response". Abdominal pain, diarrhea, and fatigue are just some common symptoms in IBD patients. The two major IBDs, ulcerative colitis and Krohn's disease, are mild for some people, but for others, they can make people weak and even endanger their lives. Stress events, such as losing a job or breaking up with a partner, usually occur before the onset of IBD. Thaiss and colleagues have found this connection. After a surge in stress, the brain sends signals to the adrenal gland, which in turn releases a chemical called glucocorticoids to other parts of the body. Initially, researchers considered the possibility of glucocorticoids directly acting on immune cells, which respond by releasing molecules that cause inflammation. But it turns out that there is still a layer of truth between the two, "Thaiss said. They found in mice that glucocorticoids act on intestinal neurons and glial cells connecting intestinal neurons. After being activated by glucocorticoids, some glial cells release molecules that trigger immune cells. Conversely, the molecules released by these immune cells are typically used to combat pathogens, but in this case, they can ultimately lead to painful intestinal inflammation. Meanwhile, researchers have found that glucocorticoids can prevent the full development of immature intestinal neurons. Therefore, these neurons only produce low levels of signaling molecules, leading to intestinal muscle contraction. This means that food moves slowly in the digestive system, which increases the discomfort of IBD. Researchers were surprised to find that glucocorticoids can cause intestinal inflammation, as these compounds are sometimes used to treat IBD. This obvious paradox can be explained by the short-term framework of using this therapy. Thaiss explained that although rapid outbreaks of glucocorticoids seem to have anti-inflammatory effects, when stress becomes chronic, the "system completely changes" and glucocorticoids begin to exert pro-inflammatory effects. John Chang, a gastroenterologist and immunologist at the University of California, San Diego, said this is a "reasonable explanation". Thaiss stated that the brain's ability to drive organ inflammation "seems much stronger than previously thought. This indicates that combining IBD treatment drugs with stress management methods may be more effective than using drugs alone. At the same time, from the brain to