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Irritable Bowel Syndrome (IBS)

Last Updated: Mar 1, 2019


Irritable bowel syndrome (IBS) is a disorder of the digestive tract characterized by recurring symptoms of abdominal pain, cramping, and excess gas associated with hard stools (constipation) or watery stools (diarrhea). IBS is not a disease; instead it is considered a functional disorder in which the intestines behave abnormally, but display no visible evidence of disease or damage to the intestinal wall. For patients, this is a long-term condition, but it is not life threatening.

Small and large intestines

IBS is the most common gastrointestinal disorder, affecting 10-15% of the adult population. It is more likely to develop in women than men, and the age of onset is typically under 45.

IBS was sometimes called spastic colon or spastic bowel, due to the presence of abnormal muscle spasms in those suffering from it. However, with greater understanding of the full nature of IBS, these terms are no longer used synonymously with this disorder, since muscle spasms are not necessarily present.

Similarly, IBS is also occasionally called nervous bowel, since the medical community recognized connections between the disorder and psychological factors such as anxiety. Because nervous bowel as a term would appear to address only some of the mental causes of IBS without the observable physical causes, the term does not adequately describe this disorder.

Irritable bowel syndrome differs from inflammatory bowel disease, in which the intestines show visible evidence of disease characterized by chronic inflammation and ulceration of the lining of the intestinal wall.

Causes and Risk Factors

The cause of IBS is unknown, but emotional stress, certain foods, and other factors exacerbate the symptoms.

Research offers the following observations:

  • Emotional stress seems to exacerbate IBS symptoms.
  • Psychological problems such as anxiety, depression, and panic attacks are more common in people with IBS.
  • Abnormal signals from the brain potentially cause intestinal dysfunction.
  • Abnormal muscle spasms of the intestinal wall may explain symptoms of abdominal pain and cramping.
  • An increased sensitivity to pain could possibly explain the abdominal discomfort.
  • Abnormally large numbers of bacteria in the small intestine (small intestinal bacterial overgrowth) may produce excess gas and diarrhea.
  • Having a relative with IBS increases a person’s chance of developing the condition.
  • Certain foods aggravate the symptoms.


With IBS, patients experience repeated episodes of lower abdominal pain, cramping, excess gas, abdominal bloating, and a change in bowel habits (either constipation or diarrhea). Some patients describe a mixture of constipation alternating with diarrhea.

There is no cure for IBS, and many patients experience recurring symptoms over the course of their lifetime.

Diagnosis and Treatment

IBS is diagnosed when a patient experiences abdominal discomfort occurring three or more times a month over a three-month period in the absence of gastrointestinal disease or injury. The diagnosis is confirmed by a normal physical examination and normal diagnostic test results.

When IBS is suspected, doctors may perform the following diagnostic tests to be sure there is no other gastrointestinal disorder to explain the symptoms:

  • Blood tests to check for anemia (low number of red blood cells).
  • Stool samples to detect intestinal bleeding or infection.
  • Lower gastrointestinal series (an X-ray to examine the large intestine).
  • Colonoscopy (a procedure which uses a flexible camera to view the colon). Alternatively, a sigmoidoscopy is a similar procedure where the doctor inspects only the lower portion of the large intestine (sigmoid colon).
  • There is also a newer option that can lead to good clarity. It’s a blood test that checks for evidence of a particular response to prior gastroenteritis or food poisoning; evidence has shown a strong connection between this and IBS (though not in all patients). The test can either be administered in a doctor’s office or at your home. Learn more about this IBS blood test and whether it’s a good option for you.

The X-rays and colonoscopy are not performed unless a patient has alarming signs and symptoms such as anemia, weight loss, and rectal bleeding. If a patient is over age 50 and has symptoms of IBS, a colonoscopy is usually performed to check for colon cancer.

Because there is no cure for IBS, the goal of treatment is to control a patient’s predominant symptoms. The cornerstones of treatment are dietary and lifestyle changes, medications, probiotics, and mental health therapy. Surgery has no benefit and should be avoided.

Dietary and Lifestyle Changes

  • Avoidance of foods that aggravate symptoms. Examples are milk, wheat, alcohol, caffeine, carbonated beverages, artificial sweeteners, red peppers, green onions, and gas-forming foods like beans and cabbage. There is no universally successful diet for IBS, so patients need to experiment with eliminating various foods.
  • High-fiber foods such as vegetables, fruits, and whole grains help soften the stool and relieve constipation.
  • Psyllium, a high-fiber dietary supplement, relieves constipation by adding bulk and softening the stool. Bloating is a potential problem with this product.
  • Exercise
  • Stress reduction
  • Relaxation techniques such as meditation
  • Avoidance of smoking


  • Laxatives treat constipation and increased bowel movements.
  • Antidiarrheal medications help stop diarrhea.
  • Antispasmodic medications decrease the muscle contractions in the bowel walls and may help relieve abdominal pain and cramping.
  • Probiotics (healthy bacteria for the gastrointestinal tract) may decrease the symptoms.
  • Certain antidepressant medications relieve pain in some patients.

Mental Health Treatment

For some patients, therapies for psychological disorders may also relieve their IBS symptoms by addressing the emotional stress and mental problems linked to the condition. Psychotherapy involves exploring a patient’s thoughts and maladaptive behaviors and identifying effective coping techniques.

Alternative Treatment

Acupuncture (an alternative therapy that involves sticking the skin with small needles) may help alleviate IBS symptoms, but further studies are needed.


The cause of IBS is not well understood and effective preventive measures are not established. Researchers believe that both physical and mental health problems impact this condition. Although there is no cure for IBS, the condition is not life threatening and symptoms can improve with a range of dietary, medical, and mental health treatments.


  • American College of Gastroenterology Task Force on Irritable Bowel Syndrome, Brandt LJ, Chey WD, Foxx-Orenstein AE, Schiller LR, Schoenfeld PS, Spiegel BM, Talley NJ, Quigley EM. An Evidence-Based Position Statement on the Management of Irritable Bowel Syndrome. Am J Gastroenterol. 2009 Jan; 104 Suppl 1:S1-35. Accessed April 10, 2014.
  • Irritable Bowel Syndrome (IBS). Cleveland Clinic website. Accessed April 10, 2014.
  • Irritable Bowel Syndrome (IBS). National Digestive Diseases Information Clearinghouse (NDDIC) website. Accessed April 10, 2014.
  • Irritable Bowel Syndrome. American College of Gastroenterology website. Accessed April 10, 2014.
  • IBS Treatment Matrix. American College of Gastroenterology website. Accessed April 10, 2014.

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Tina Shahian, PhD

Tina is a writer for Innerbody Research, where she has written a large body of informative guides about health conditions.


A communication specialist in life science and biotech subjects, Tina’s successful career is rooted in her ability to convey complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. Tina Shahian’s Linkedin profile.


In her spare time, Tina enjoys drawing science-related cartoons.