What causes IBS?

The causes of IBS are not well understood. Researchers believe a combination of physical and mental health problems can lead to IBS. The possible causes of IBS include the following:

  • Brain-gut signal problems.
  • GI motor problems.
  • Hypersensitivity.
  • Mental health problems.
  • Bacterial gastroenteritis.
  • Small intestinal bacterial overgrowth (SIBO).
  • Body chemicals.
  • Genetics.
  • Food sensitivity.

IBS - Irritable bowel syndrome

Irritable bowel syndrome is a functional gastrointestinal (GI) disorder, meaning it is a problem caused by changes in how the GI tract works. People with a functional GI disorder have frequent symptoms, but the GI tract does not become damaged. IBS is not a disease; it is a group of symptoms that occur together. The most common symptoms of IBS are abdominal pain or discomfort, often reported as cramping, along with diarrhea, constipation, or both. In the past, IBS was called colitis, mucous colitis, spastic colon, nervous colon, and spastic bowel. The name was changed to reflect the understanding that the disorder has both physical and mental causes and is not a product of a person’s imagination.

IBS is diagnosed when a person has abdominal pain or discomfort at least three times per month for the last 3 months without other disease or injury that could explain the pain. The pain or discomfort of IBS may occur with a change in stool frequency or consistency or may be relieved by a bowel movement.

IBS is often classified into four subtypes based on a person’s usual stool consistency. These subtypes are important because they affect the types of treatment that are most likely to improve the person’s symptoms.

What are the symptoms of IBS?

The symptoms of IBS include abdominal pain or discomfort and changes in bowel habits. To meet the definition of IBS, the pain or discomfort should be associated with two of the following three symptoms:

  • start with bowel movements that occur more or less often than usual
  • start with stool that appears looser and more watery or harder and more lumpy than usual
  • improve with a bowel movement

Other symptoms of IBS may include

  • Diarrhea—having loose, watery stools three or more times a day and feeling urgency to have a bowel movement
  • Constipation—having hard, dry stools; three or fewer bowel movements in a week; or straining to have a bowel movement
  • Feeling that a bowel movement is incomplete
  • Passing mucus, a clear liquid made by the intestines that coats and protects tissues in the GI tract
  • Abdominal bloating