U.S. Department of Health and Human Services

Definition and Facts for Irritable Bowel Syndrome

What is IBS?

Irritable bowel syndrome (IBS) is a group of symptoms—including pain or discomfort in your abdomen and changes in your bowel movement patterns—that occur together. Doctors call IBS a functional gastrointestinal (GI) disorder. Functional GI disorders happen when your GI tract behaves in an abnormal way without evidence of damage due to a disease.

Does IBS have another name?
In the past, doctors called IBS colitis, mucous colitis, spastic colon, nervous colon, and spastic bowel. Experts changed the name to reflect the understanding that the disorder has both physical and mental causes and isn’t a product of a person’s imagination.

What are the four types of IBS?

Doctors often classify IBS into one of four types based on your usual stool consistency. These types are important because they affect the types of treatment that are most likely to improve your symptoms.

The four types of IBS are

  • IBS with constipation, or IBS-C
    • hard or lumpy stools at least 25 percent of the time
    • loose or watery stools less than 25 percent of the time
  • IBS with diarrhea, or IBS-D
    • loose or watery stools at least 25 percent of the time
    • hard or lumpy stools less than 25 percent of the time
  • Mixed IBS, or IBS-M
    • hard or lumpy stools at least 25 percent of the time
    • loose or watery stools at least 25 percent of the time
  • Unsubtyped IBS, or IBS-U
    • hard or lumpy stools less than 25 percent of the time
    • loose or watery stools less than 25 percent of the time

How common is IBS?

Studies estimate that IBS affects 10 to 15 percent of U.S. adults.1However, only 5 to 7 percent of U.S. adults have received a diagnosis of IBS.2

 

Who is more likely to develop IBS?

IBS affects about twice as many women as men and most often occurs in people younger than age 45.1

What other health problems do people with IBS have?

People with IBS often suffer from other GI and non-GI conditions. GI conditions such as gastroesophageal reflux disease and dyspepsia are more common in people with IBS than the general population.
 
Non-GI conditions that people with IBS often have include

1Grundmann O, Yoon SL. Irritable bowel syndrome: epidemiology, diagnosis, and treatment: an update for health-care practitioners. Journal of Gastroenterology and Hepatology. 2010;25:691–699.

2Irritable bowel syndrome. American College of Gastroenterology website. www.patients.gi.org/topics/irritable-bowel-syndrome. Accessed September 2, 2014.

​​​​​​​
​February 23, 2015​​​​

Digestive Disease Organizations

Many organizations provide support to patients and medical professionals. View the full list of Digestive Disease Organizations​​ (PDF, 341 KB)​​​​​

Contact Us

Health Information Center