Possible causes of Irritable Bowel Syndrome

Several possible causes of IBS are being considered:

• Use of analgesics: In survey studies, researchers have found that acetaminophen, the ingredient in Tylenol, has been frequently used by people who develop IBS-diarrhea. This drug is known to cause elevated levels of serotonin, and research indicates that serotonin may become elevated in patients with IBS-diarrhea after eating
• Brain-bowel chemical imbalance: The brain and the gut are intimately connected by both the nervous system and by neurotransmitter chemicals, such as serotonin and norepinephrine. Both chemicals may be involved with the production of IBS symptoms. So far, we know that diarrhea can occur when high amounts of serotonin inhibit norepinephrine and cause levels of acetylcholine to increase. On the other hand, when norepinephrine levels increase, the result is constipation, as well as a lowering of serotonin levels and blockage of acetylcholine. For IBS patients, this chemical dance may lead to the fluctuating bowel symptoms of constipation and diarrhea. But we must ask what the cause of the imbalance is in the first place.
• Female hormones: Considering that men don’t have high amounts of female hormone, and men do suffer from IBS, female hormones are not the cause of IBS. However, women have twice the incidence of IBS as men.