Everyone has had irritable bowel syndrome at one time or another. Your entire digestive system from the rear of your mouth (actually the lower two-thirds of your esophagus) to the top of your rectum is under autonomic control. By that I mean that you have absolutely no voluntary control over the rate of progress of food through your digestive tract. All the muscles involved are smooth muscle, and are controlled by a complicated interaction between your sympathetic and parasympathetic nervous systems as well as a host of secretory hormones. There is also a constant interplay between the spinal nerves and the muscles and digestive enzymes of the gut, with modifications superimposed by the vagus nerve from the brain and the secretion of adrenalin.
We all have heard the expressions, and many of us have felt the sensation of "made me sick to my stomach", "made me throw up", "turned my stomach" "gave me agida or heartburn", "left a sour taste in my mouth", "my mouth turned dry", or "my mouth watered" , and thus are aware of the mind-body connection between our brain and our gut. The validity of these expressions was verified beginning in April, 1822. A French trapper, Alexis St. Martin, was accidentally shot in the stomach on Mackinac Island, Michigan, and healed by a Dr. William Beaumont. The healing left a hole directly into his stomach through the abdominal wall. Dr. Beaumont performed many experiments which he documented, including observing the color of the interior of the stomach wall, and the rate of digestion of a piece of meat dangled on a string into the stomach through the hole. He observed that when the patient got angry or upset, the stomach wall blanched indication a decreased blood supply, and the stomach muscles either stopped squeezing back and forth, or went into spasm. Under normal conditions, the stomach wall was pink. When he lowered a piece of meat into the stomach, the walls became red as the local blood flow increased, gastric juice was secreted, and gastric peristalsis was stimulated. If he made him angry or upset during this process, the gastric juice secretion and peristalsis markedly decreased and the stomach color grew paler.
Problems at the other end of the gut can also develop during stress. Some people develop diarrhea. Others become constipated. Often young children who are angry involuntarily refuse to move their bowels for one or two weeks or even longer. (The recorded record for an adult is a year and a day, and an operation was required, with the use of a hammer and chisel.)
One way to recognize the presence of IBS is to realize that disease is not cognizant of time, or the day of the week, or geography. So if you have GI problems during the week and not on weekends, maybe your job is stressing you out. If your stomach problems magically disappear when you are away on vacation, then maybe your daily responsibilities are causing a problem. Similarly, most people sleep very well on vacation, almost as if their insomnia decided to take a vacation along with their body. And of course if visiting someone or that someone visiting you distresses your gut, then that person is toxic for you for whatever reason. When your emotions are stressed your brain reacts by causing distress in your body, typically in your gut, and this is the brain's way of crying for help and relief.
And for the individual with functional bowel problems who says "I have nothing to feel stressed about", one can only hope that a kind and understanding family physician can help that person to understand the amazingly powerful mind-body connection.