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Conditions InDepth: Irritable Bowel Syndrome (IBS)

Irritable bowel syndrome (IBS) is a range of symptoms that happen at the same time. Belly pain, cramping, gas, bloating, and changes in bowel habits are the most common issues. Pain from IBS is often better after a bowel movement.

The Intestines

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Causes of IBS

IBS is a functional disorder that affects the intestines. The exact cause is unknown. Nerves, muscles, air, and movement all help the intestines work smoothly. One or more problems in any of these pathways can lead to IBS. Increased sensitivity in your intestines can be influenced by:

  • Infection or inflammation
  • Changes in the normal bacteria of the intestines—may lead to more gas production
  • Certain foods
  • Stress, anxiety, or depression
  • Missing enzymes that breakdown certain sugars—present from birth (rare)

Types of IBS

IBS types are based on the bowel habit that is causing the most problems:


Definition and facts for rritable bowel syndrome. National Institute of Diabetes and Digestive and Kidney Diseases website. Available at: Updated November 2017. Accessed June 7, 2019.

Ford AC, Lacy BE, Talley NJ. Irritable bowel syndrome. N Engl J Med. 2017;376(26):2566-2578.

Irritable bowel syndrome (IBS). EBSCO DynaMed Plus website. Available at: Updated September 10, 2018. Accessed June 7, 2019.

Wilkins T, Pepitone C, Alex B, Schade RR. Diagnosis and management of IBS in adults. Am Fam Physician. 2012;86(5):419-426.

Last reviewed December 2018 by EBSCO Medical Review Board Daus Mahnke, MD  Last Updated: 6/7/2019