May 18, 2021
Written by: Lindsay Ejoh
Have you ever had butterflies in your stomach when thinking of someone special? Or felt like you had to poop before taking a big exam? If so, you’re already aware that your gut is very sensitive to your emotions, especially stress.
The gastrointestinal tract, which comprises the esophagus, stomach, and intestines, has nerves that run along its entire length. The gut is sometimes referred to as “the second brain” because it is considered to have its own nervous system, called the enteric nervous system (ENS)1. The ENS contains the most neurons in one location outside the brain itself.
The ENS can even operate completely independently from the brain. If the intestines are removed from the body, they would still contract and push food through, despite losing their connection with the brain and spinal cord! Though it has the potential to operate independently, your gut typically has multiple connections with the brain. These gut-brain connections are bidirectional, and can explain how painful signals from the gut can be perceived by your brain, and how stress and anxiety can impact gut function. The gut-brain axis was discussed further in a previous NeuroKnow article, A Gut Feeling.
Stress is your body’s natural reaction to threatening situations, and involves activation of the sympathetic nervous system, or the “fight or flight” response. When under stress, the brain signals the production of cortisol, a hormone that acts throughout the body to make you alert and ready to take action. In preparation for a response to the threat, your body provides extra energy to parts of your body that might need it, like muscles in the arms and legs, and diverts resources from less urgent bodily functions, such as digestion. This causes changes in gut movement patterns that can trigger pain, cramps, constipation, diarrhea, and nausea2. Evolutionarily, it is advantageous for our bodies to respond this way to stress, as it must have helped our ancestors avoid predators, promoting survival. However, the stressors we face today may not be as acute as an attacking animal or dangerous landscape, though our stress response remains similar.
Sustained stress negatively impacts gut health. Stress often induces visceral pain, which is pain felt in your abdominal organs. This sensation differs from pain felt on the skin, as it is not specific to a particular area. This diffuse pain is why damage to the bladder, kidneys, stomach, pancreas, etc are all felt broadly as “abdominal pain.” Patients with Irritable Bowel Syndrome (IBS) often have overlapping stress disorders like depression, anxiety, and post-traumatic stress disorder3. To make matters worse, stress can worsen the symptoms of IBS. Stress is often thought to be a negative mental state, and the effect of stress on bodily function can often be overlooked. Next time you notice a difference in bowel movements, appetite, or sensitivity to certain foods, trust your gut! Your body may be sending you a message that your stress levels are higher than normal.
- Furness, J. B. (2012). The enteric nervous system and neurogastroenterology. Nature Reviews Gastroenterology & Hepatology, 9(5), 286–294. https://doi.org/10.1038/nrgastro.2012.32
- Kevin Dolehide, D. O. (2020). Stress and stomach pain: When should you see a specialist? UChicago Medicine. https://www.uchicagomedicine.org/forefront/gastrointestinal-articles/stress-and-stomach-pain-when-should-you-see-a-specialist#:~:text=Why%20does%20stress%20cause%20stomach,diarrhea%2C%20nausea%20and%20other%20symptoms.
- Meerveld, B. G.-V., & Johnson, A. C. (2018). Mechanisms of Stress-induced Visceral Pain. Journal of Neurogastroenterology and Motility, 24(1), 7–18. https://doi.org/10.5056/jnm17137