The connection between the gut and the brain, known as the gut-brain axis, has drawn increasing scientific interest for its role in health and disease. Dr. Eamonn Quigley, a gastroenterologist at Houston Methodist, explained how this bidirectional communication affects both physical and mental well-being.
“The gut has sensory nerves, and they transmit messages through the spinal cord, through the vagus nerve, to the brain, where then they’re recognized and if the brain decides so, acted upon by the brain sending signals down to the gut leading to changes in gut motility or secretion,” Dr. Quigley said.
He noted that sometimes the brain influences gut activity—such as when stress leads to digestive symptoms like diarrhea or nausea—while at other times symptoms originate in the gut and affect mood or anxiety levels. “In some situations, it can be the brain predominantly influencing the gut,” he said. “In other situations, it can be the gut influencing the brain.”
Conditions such as irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), including Crohn’s disease and ulcerative colitis, are closely tied to this axis. For example, people with chronic gastrointestinal pain may also develop anxiety or depression; these psychological states can then worsen their digestive symptoms.
Dr. Quigley emphasized that “pain of virtually any origin will have a gut-brain element to it.” He added that understanding this paradigm is essential because it plays a role in many bodily functions beyond digestion—including immunity, metabolism, hunger regulation, behavior, cognitive function and pain tolerance.
The gut microbiome—the collection of bacteria and other microorganisms living in our digestive tract—is now recognized as an integral part of this axis. It interacts constantly with both digestion processes and neurological responses.
Regarding treatment options for conditions linked to the gut-brain axis like IBS or IBD, Dr. Quigley highlighted mind-gut interventions: “Mind-gut interventions are extremely beneficial…from medications like antidepressants or antianxiety drugs…to behavioral therapies.” These medications often work not by treating depression directly but by affecting sensory input from the gut. Behavioral therapies such as cognitive behavioral therapy (CBT), hypnotherapy and mindfulness practices have shown efficacy for patients whose symptoms are influenced by psychological factors.
Vagus nerve stimulation—a technique involving electrical pulses delivered to a key nerve connecting brain and body—has been used for certain neurological disorders since 1997 but is not widely adopted yet for gastrointestinal issues due to limited evidence supporting its effectiveness in that context.
The use of probiotics has also gained attention for potentially modulating mood via changes in microbiome composition. “There is data…to show that by modulating the microbiome with a probiotic…you can influence symptoms like depression and anxiety,” Dr. Quigley stated regarding research conducted at Houston Methodist.
Maintaining a healthy weight along with dietary patterns rich in fiber—such as those found in Mediterranean diets—and staying hydrated are recommended strategies for supporting optimal GI function according to Dr. Quigley’s advice. He also warned against smoking due to its association with increased risk of GI diseases including Crohn’s disease and certain cancers.
“If we were aware of these signals [between brain and gut], we’d have pain, bloating and nausea all the time,” Dr. Quigley said about why most people do not notice normal digestive processes unless something goes wrong within this complex communication network.
