Some researchers believe that the issue in IBS lies in the brain-gut connection, a mysterious link whereby the goings-on in a person’s gut are believed to influence not only mood, but some of the core facets of personality. The connection is why people feel nauseated, for example, before giving an important speech. The brain sends signals to the gut, such as, what if I mess up, and all my great auntie’s prophecies of failure and depravity come true? To which the gut responds with butterflies or violent, vomitous stage fright. Or instead, the gut might signal food poisoning! to the brain, to which the brain responds with, that hurts, and, quick find a bathroom!
Scientists have suspected this connection as far back as 1902, when a study showed that food moved differently through cats’ digestive tracts when dogs were growling at them. In 1921, the physician John Newport Langley laid the foundation for our understanding of the enteric nervous system (ENS), a collection of neurons—some 100 million—that spans from the esophagus to the rectum and sends signals, like those butterflies, to the brain. But it wasn’t until later, in 1996, when Michael Gershon, a pioneer in the field of neurogastroenterology at Columbia University, dubbed the ENS as the human body’s “second brain” that the extent, and eeriness, of the connection took hold.
The ENS is thought to use some of the same neurotransmitters, like serotonin, as the big brain in our heads. Researchers have long believed that imbalances in serotonin in the brain influence mood and cause depression, and the same can be said for the gut. The gut produces serotonin as well, and an imbalance there could be considered a kind of depression of the second brain. But the result isn’t a gut that feels sad—instead, it’s a person who could develop severe, and lifelong, depression.
One emerging theory for IBS is that there is, in fact, an imbalance of serotonin in the gut: Those with diarrhea have too much, those with constipation have too little, and both run the risk of serotonin-induced mood swings.
At a particularly low point, I Googled “IBS symptoms” and discovered some forums dedicated to IBS sufferers and others with gastrointestinal disorders. On one, an anonymous person wrote: “It seems that my whole life is dominated by my bowel to the extent that some days I am afraid to leave the house.” Another person lamented the disorder’s invisibility: “This disease does not 'show' on the outside, so even good friends are not always understanding. I am aware of this so I keep it to myself.” IBS is not a life-threatening disorder, but some people become incapacitated by it. They quit work, stop traveling, and withdraw completely. Some fall into a deep depression that exacerbates the brain-gut feedback loop and intensifies their symptoms.