The exact causes of IBS are unknown. IBS is a diagnosis of exclusion, which means that other diseases and infections must be ruled out before it can be diagnosed.
Potential causes of IBS may include sensitivity of the GI tract to gas and bloating, changes in the microbiome (organisms in the gut), or changes in the levels of specific compounds or chemicals within the body, such as serotonin—a chemical in the body that helps regulate mood and social behavior. Although stress does not cause IBS, many people with IBS notice that stress does aggravate their symptoms. Having IBD or a recent GI tract infection (like gastroenteritis) can increase the risk for developing IBS. IBS does not have clear causes, but a number of factors are thought to play a role.
- Acute GI infection – Approximately 20-30% of IBS cases are triggered by an acute gastroenteritis infection. Additional risk factors are young age, prolonged fever, anxiety, and associated depression
- Stress, depression and anxiety – These have not been shown to cause or influence the onset of IBS, but may play a role in the persistence and perceived severity of symptoms
- Bacterial imbalance – Small intestinal bacterial overgrowth (SIBO) occurs with greater frequency in people who have been diagnosed with IBS. Alterations in gut bacteria may also be responsible.
- Altered gastrointestinal motility – Dysfunction in the movement of food particles through the colon and an exaggerated gut response to eating or drinking may also play a major role in IBS. There is an increasing focus on new diet regimes, such as low FODMAP or gluten free diets, which have helped many people with controlling their IBS symptoms.
- Genetic and environmental – Some individuals may be predisposed to digestive disorders such as IBS.
“Symptoms and Causes of Irritable Bowel Syndrome”. NIDDK. February 23, 2015.