I've had bad IBS since the late '90s beginning after an intestinal infection (the only thing I know is 'not e-Coli') that gave me a white cell count of 25. I fought going to the hospital and the gastro-ent who was dealing with me then was one of those who believes in keeping prescription antibotics to a minimum so he said, "You're getting better yourself. Just stay home and in bed until you're better." Two months later I was long back to teaching but still feeling ill and queasy all too often. Over the years it got worse, compounded by the fact that I had developed a spontaneous allergy to high-proof alcohol 20 years before and, although I was still drinking wine and highly diluted spirits, I think that allergy was beginning to affect the mucus membrane in the intenstine as well.
I started having regular colonoscopies at 50--ten years ago--and there was no sign of IBD or cancer so the new GI doc called what I was suffering from IBS. It was often accompanied by spontaneous projectile vomiting and he explained it like this: When you consume a food that is going to irritate the bowel lining (tends to be caffeine, chocolate, alcohol, carbonated drinks, non-soluable fiber, spicy foods and even yogurt), it causes you to feel the peristaltic contractions of the bowel, which are a normal part of digestion (in fact, I think there's even a definition of IBS which defines the problen as exactly that: feeling the peristaltic contractions as pain when others barely feel them at all--why it gets worse with stress, is more prevalent in women, and bad IBS is often a result--as is mine--of a serious intestinal infection), as pain (or 'cramping'). If you eat a significant amount of food (or one of the IBS triggers) when the intestine is in that sensitive state, the digestive tract--which is all of a piece--says, 'Uh-uh, we can't handle more of this.' So if you can't move it out the proper end of the intestine fast enough and the IBS pain persists and gets worse, the diaphragm contracts and pushes out the stomach contents through the esophagus--no nausea, you feel immediately better and usually the peristaltic contractions (cramping) stop shortly thereafter. The vomiting is projectile because of the vehemence of the diaphragm's contractions.
So I totally gave up alcohol and tried to avoid the others. But the GI sent me to a couple of surgeons because he believed a narrowing in part of the bowel and inflammation he saw during one of the colonoscopies was diverticulitis. Two surgeons later, that was a no (probably a histamine reaction, said one, because I had not yet given up diluted alcohol totally)--but in the interim I had been sent for CT scans by both. I was terrified of the results because there is ovarian cancer in the family. I had a GP's prescription for extremely low-dose clonazepam (.5 mg) for anxiety whenever, which I rarely took. But the CT scan scared me so much, I started taking 3 or 4 a day just before and for a couple of weeks after. AND the symptoms of my IBS, which were better or worse on a pretty well day-to-day basis and had been for years, WENT AWAY!!
When I asked my GP if this made sense, she said, "Of course" and I've been prescribed at least 2 pills a day ever since--I take more under stress or food mistakes--"as needed", says the prescription.
But the surprise came from my GI doc. He'd been flailing about without giving me much help--he'd been talking about an enzyme supplement that had just come out. So when I told him about the effects of clonazepam, he too said it made sense. When I asked in astonishment why then he hadn't tried that himself, he tapped his head as if I were a crazy person and said, "Because I don't treat this." Presumably he meant mental conditions.
I am a woman--now over 60--and I suffered too long and then had to stumble on help for myself. The fact that an anti-anxiety drug has some effect on bad IBS symptoms points to that definition I mentioned earlier: that for one reason or another we sufferers feel what is a normal bodily function as pain, especially in the presence of the wrong foods or too much food. Though stress or a big meal will sometimes bring on symptoms, including but much more rarely, the projectile vomiting, largely I feel it's under control. Sure there's a lot of things I can't eat and there's little point in my going to an all-you-can-eat buffet because I have to eat small meals more frequently or I will get the 'cramping' and possibly the vomiting. I'm not cured but the suffering is in my control.
I posted this because it's taken me a long time to understand the nature of IBS as I experience it. I hope this helps someone else.