What is irritable bowel syndrome (IBS)?

Irritable bowel syndrome (IBS) affects the large intestine and causes a lot of abdominal pain and discomfort. You may also experience constipation, bloating and diarrhea.

IBS is a common disorder that causes both diarrhea and constipation, bloating and abdominal pain.

Irritable Bowel Syndrome (IBS) refers to pain in the abdomen and a change in bowel habits.

Irritable bowel syndrome (IBS) is a condition that causes lower abdominal pain, along with changes in bowel habits.

IBS is a very common and frustrating condition because of the symptoms: bloating, cramping, pain. Some people experience constipation with irritable bowel syndrome, while others experience the opposite effect and develop diarrhea.

And some people flip-flop between the two extremes, living in a world where one moment they couldn’t poop if they tried and the next moment they couldn’t stop it if they wanted to. People with IBS experience some dysfunction of the immune and nervous systems that regulate the lining of the bowel (called the epithelium), which controls the flow of fluids into and out of the intestines.

When stuff moves too quickly from start to finish, the intestines can’t absorb fluids from it (hence diarrhea). And when the last meal moves too slowly, the bowel absorbs too much fluid (hence constipation). People with IBS have abnormally low levels of serotonin, most of which is produced in your gut, not your brain.

This causes all kinds of digestive problems and makes these people more susceptible to feeling pain when those problems arise.

Irritable bowel syndrome (IBS)—also known as spastic colon, spastic colitis, mucous colitis and nervous or functional bowel—occurs when the colon does not contract normally (that is, with smooth, rhythmic contractions). Instead, it seems to contract in a disorganized and sometimes violent manner. The contractions may last for prolonged periods of time. You may also experience abdominal discomfort or pain that moves around the abdomen rather than remaining localized in one area.

IBS is a chronic functional gastrointestinal disorder. It is characterized by a group of symptoms including lower abdominal pain and a change in bowel habits. Symptoms vary in different individuals and may vary from time to time in severity in the same person. IBS symptoms may be similar to those of organic/structural gastrointestinal diseases. Although there is no specific blood, X ray or endoscopic test, it is not a diagnosis of exclusion. There are specific criteria that define IBS and are used in its diagnosis as noted below.

Irritable bowel syndrome (IBS) is a gastrointestinal tract disorder that is found in approximately 10% to 20% of adults. IBS affects women slightly more often than men. (This answer provided for NATA by the University of Montana Athletic Training Education Program.)

Irritable bowel syndrome is a "functional" gastrointestinal (stomach/intestines) problem that usually presents with abdominal pain and a change in bowel habits without an underlying "pathology"—for example, these patients don't have inflammatory bowel disease, IBD, celiac disease, colon cancer, etc. For this reason, the above diagnoses need to be ruled out, and if you are having symptoms that seem like they could be irritable bowel syndrome, you should talk to your doctor.

Irritable bowel syndrome (IBS) is medically defined as "abdominal pain or discomfort that occurs in association with altered bowel habits over a period of at least three months." If you have IBS, you probably recognize it as recurrent bouts of constipation, diarrhea, or both, as well as abdominal pain, bloating, and gas. IBS hasn't been attributed to an underlying disease process or structural abnormality. It is thought to involve various, often interacting, factors—infection, faulty brain-gut communication, heightened pain sensitivity, hormones, allergies, and emotional stress. There's no cure for IBS, but there are many options for treating it, depending on your predominant symptoms.

Irritable bowel syndrome (IBS) is a common health condition that involves chronic abdominal discomfort or pain, bloating and changes in bowel habits. It can also lead to a tired feeling and mild depression.

Some people with IBS have constipation, others have diarrhea and some experience bouts of both. Symptoms associated with IBS include bloating, passage of mucus or straining with bowel movements, a sense of incomplete evacuation after bowel movements or a sense of urgency to move the bowels.

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Irritable bowel syndrome (IBS) is a disorder involving the lower intestinal tract. It involves abdominal pain, as well as alternating constipation and diarrhea. IBS is a common disorder and happens more often in women than men. Although IBS can cause a great deal of discomfort, it does not harm the intestines. No one knows the exact cause, and there is no specific test for IBS. However, your doctor may run tests to be sure you don't have other diseases. Most people diagnosed with IBS can control their symptoms with diet, stress management and medicine.

Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

The constant pain, gas, bloating, disturbed defecation, and uncertainty that plagues people with irritable bowel syndrome (IBS) is deeply disabling. The unpredictable course of the disease makes people with IBS expert bathroom-mappers, constantly on the lookout in case the urge comes suddenly.

Irritable bowel syndrome is considered a gastrointestinal functional disorder, meaning that the natural rhythmic movement of the gut is flawed. It is the most common syndrome seen by gastroenterologists and keeps more people holed-up at home than the common cold.

Dr. William B. Salt, MD

Irritable bowel syndrome (IBS) is one of many functional symptom syndromes composed of medically unexplained symptoms, which are “caused” by dysfunction involving the mind/brain—body connection.

To explain the unexplainable and cause, look at the terms used here and then “see the big picture.”


  • Functional refers to how the body works.
  • Symptoms include chronic/recurrent abdominal pain and discomfort associated with bowel function.
  • Symptom Syndromes are collections of medically unexplained symptoms. They are also known as functional somatic syndromes and chronic multisymptom illnesses. Nearly every specialty defines at least one syndrome. Examples include RHEUMATOLOGY (fibromyalgia) and GASTROENTEROLOGY (irritable bowel syndrome).
  • Medically Unexplained Symptoms (MUS) cannot be explained by medical tests, such as x-rays, endoscopies, and blood tests, because they are caused by dysfunction.
  • Dysfunction is disturbance or “malfunction” of how the body works.
  • Mind/Brain-Body Connection refers to how the mind/brain and body communicate and talk with one another.

MUS and symptom syndromes frequently overlap with one another and are commonly associated with and often attributed to stress, depression, and anxiety. Research is showing how the mind/brain and body communicate and both how and why symptoms are generated. For example, the "central" (mind/brain) can become "sensitized" to "peripheral" (body) pain and symptom signals sent in response to stressors in the environment. So these symptom syndromes are now being called, central sensitivity syndromes.

This author and Thomas L Hudson propose a new unifying and holistic medical model of medically unexplained symptoms and their related symptom syndromes as chronic disease, explain both how and why they occur and are often associated with stress and depression, and show what people can do to help themselves and work effectively with their caregivers (

DISEASE IS DYSFUNCTION, AND SYMPTOMS ARE THE EXPRESSION. The cause of medically unexplained symptoms and pain can be understood as disease/dysfunction, regardless of whether the symptoms are widespread (e.g., the pain and fatigue of fibromyalgia) or localized to a specific area of the body (e.g., the colon of irritable bowel syndrome).

In IBS, stressor/triggers include stress, psychological distress, dietary factors, and may involve gut bacteria.

Patsy Catsos
Nutrition & Dietetics Specialist

IBS stands for Irritable Bowel Syndrome. This condition can be defined as "abdominal pain and discomfort with altered bowel habits in the absence of any other mechanical, inflammatory, or biochemical explanation for these symptoms." IBS itself is not a disease, but a collection of symptoms. IBS is often considered a "diagnosis of exclusion." That means it is usually diagnosed after other gastrointestinal disorders and diseases have been ruled out.

IBS: Free at Last! Change Your Carbs, Change Your Life with the FODMAP Elimination Diet, 2nd Edition

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IBS: Free at Last! Change Your Carbs, Change Your Life with the FODMAP Elimination Diet, 2nd Edition

IBS should not make you skip a beat—get your groove back! Tired of missing the fun because of your irritable bowel syndrome (IBS)? Confused about what to eat? Think you’re the only one who feels...
Dr. Lawrence S. Friedman, MD

A common intestinal disorder with a myriad of unpleasant symptoms is irritable bowel syndrome (IBS). IBS affects millions of people, but its cause is unclear and treatment is often a trial-and-error process that may or may not be successful. It is the most common diagnosis made by gastroenterologists and accounts for as many as 3.5 million physician visits and 2.2 million prescriptions per year. Irritable bowel syndrome may well be the most challenging functional gastrointestinal (GI) disorder for patients and doctors alike. Several studies have found that patients with IBS have a significantly lower quality of life than patients without the syndrome and that the illness is seriously underdiagnosed. Through the years, IBS has been called by many names—spastic colon, spastic bowel, colitis, mucous colitis, and functional bowel disease. None of these names is quite accurate.

A survey of 1,713 people who met the criteria for IBS found that 22% had IBS symptoms for more than 10 years, and another 41% had experienced symptoms for one to five years. Sixty-seven percent said their most recent episode occurred within the past three months. Ninety-one percent had used at least one over-the-counter medication for IBS during the past year, and 46% had used at least one prescription drug. Over all, they scored lower than the average for the U.S. population in all quality of life categories surveyed, including bodily pain, general health, vitality, social functioning, and mental health. All in all, too many people are suffering from this perplexing condition.

If you have some of the symptoms of IBS, you may need to seek medical attention if you are truly miserable or worried about the possibility of more serious illness. However, there may be good reason not to seek medical attention; the cost of such care can be high. In rare cases, IBS patients undergo unnecessary surgery. And the drugs used to treat IBS are costly, even though studies have not proved most of them to be more effective than placebos. On the other hand, studies have shown that any drug used to treat an IBS patient exhibits a strong placebo effect.

Dr. Patricia Raymond, MD

Irritable bowel syndrome (IBS) is diagnosed by a description of symptoms, as there is no blood, x-ray, biopsy, or endoscopic test that positively diagnoses the disorder. A group of researchers into this functional bowel disorder went off to Rome some years ago, and in conference developed the “Rome Criteria” for the diagnosis of irritable bowel syndrome.

IBS is a chronic, episodic medical condition characterized by abdominal pain or discomfort associated with altered bowel function (at least two of the three):

  • Less than three bowel movements per week or greater than three per day
  • Hard or lumpy stools, or loose or watery stools
  • Straining with a bowel movement, or urgency, or a feeling of incomplete evacuation

Let’s be clear here. If you don’t have abdominal pain associated with your strange poops you may have just diarrhea or constipation, not IBS. If you have belly pain but no strange poops, it isn’t IBS. Both must travel together. You need to have had the condition chronically (greater than six months), but not continuously. You should have experienced it for at least 12 weeks over any 12-month period. And, you need to have no other bowel disorder. If you have inflammatory bowel disease, like Crohn's disease or ulcerative colitis, you don’t have IBS. IBS occurs in the absence of other disorders.

To confuse you further, there are three subgroups of IBS. The folks with D-IBS and C-IBS get, well, loose or constipated poops respectively. Then there’s a group of poor souls that are what we call “alternators”, who swing from D-IBS to C-IBS with wild abandon.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.