The exact cause of irritable bowel syndrome (IBS) isn't known. But health experts believe that faulty communication between the brain and the intestinal tract is one cause of symptoms. In some people, this miscommunication causes abnormal muscle contractions or spasms, which often cause cramping pain. The spasms may speed the passage of stool, causing diarrhea. Or they may slow it down, causing constipation or bloating.
Many people who have IBS seem to have unusually sensitive intestines. It isn't known why their intestines are more likely to react strongly to the elements that contribute to IBS. People who have IBS may start having symptoms because of one or more factors, including:
- Eating (though no particular foods have been linked with IBS).
- Stress and psychological issues, such as anxiety and depression.
- Hormonal changes, such as during the menstrual cycle.
- Some medicines, such as antibiotics.
- An infection in the digestive tract, such as salmonella.
- Genetics. IBS may be more likely to occur in people who have a family history of the disorder.