Overview

Irritable bowel syndrome (IBS) is a common condition that affects the stomach and intestines, also called the gastrointestinal tract. Symptoms include cramping, belly pain, bloating, gas, and diarrhea or constipation, or both. IBS is an ongoing condition that needs long-term management.

Only a small number of people with IBS have severe symptoms. Some people can control their symptoms by managing diet, lifestyle and stress. More-severe symptoms can be treated with medicine and counseling.

IBS doesn't cause changes in bowel tissue or increase risk of colorectal cancer.

Symptoms

Symptoms of IBS vary but are usually present for a long time. The most common include:

  • Belly pain, cramping or bloating that is related to passing stool.
  • Changes in appearance of stool.
  • Changes in how often you are passing stool.

Other symptoms that are often related include sensation of incomplete evacuation and increased gas or mucus in the stool.

When to see a doctor

See a healthcare professional if you have a persistent change in bowel habits or other symptoms of IBS. They may mean a more serious condition, such as colon cancer. More-serious symptoms include:

  • Weight loss.
  • Diarrhea at night.
  • Rectal bleeding.
  • Iron deficiency anemia.
  • Unexplained vomiting.
  • Pain that isn't relieved by passing gas or stool.

Causes

The exact cause of IBS isn't known. Factors that appear to play a role include:

  • Muscle contractions in the intestine. The walls of the intestines are lined with layers of muscle that contract as they move food through the digestive tract. Contractions that are stronger and last longer than usual can cause gas, bloating and diarrhea. Weak contractions can slow food passage and lead to hard, dry stools.
  • Nervous system. Issues with the nerves in the digestive system may cause discomfort when the belly area, called the abdomen, stretches from gas or stool. Poorly coordinated signals between the brain and the intestines can cause the body to overreact to changes that typically occur in the digestive process. This can result in pain, diarrhea or constipation.
  • Severe infection. IBS can develop after a severe bout of diarrhea caused by bacteria or a virus. This is called gastroenteritis. IBS also might be associated with a surplus of bacteria in the intestines, known as bacterial overgrowth.
  • Early-life stress. People exposed to stressful events, especially in childhood, tend to have more symptoms of IBS.
  • Changes in gut microbes. Examples include changes in bacteria, fungi and viruses, which typically live in the intestines and play a key role in health. Research indicates that the microbes in people with IBS might differ from those in people who don't have IBS.

Triggers

Symptoms of IBS can be triggered by:

  • Food. The role of food allergy or intolerance in IBS isn't fully understood. A true food allergy rarely causes IBS. But many people have worse IBS symptoms when they eat or drink certain foods or beverages. These include wheat, dairy products, citrus fruits, beans, cabbage, milk and carbonated drinks.
  • Stress. Most people with IBS experience worse or more-frequent symptoms during periods of increased stress. But while stress may make symptoms worse, it doesn't cause them.

Risk factors

Many people have occasional symptoms of IBS. But you're more likely to have the syndrome if you:

  • Are young. IBS occurs more often in people under age 50.
  • Are female. In the United States, IBS is more common among women. Estrogen therapy before or after menopause also is a risk factor for IBS.
  • Have a family history of IBS. Genes may play a role, as may shared factors in a family's environment or a combination of genes and environment.
  • Have anxiety, depression or other mental health issues. A history of sexual, physical or emotional abuse also might be a risk factor.

Complications

Long-lasting constipation or diarrhea can cause hemorrhoids.

In addition, IBS is associated with:

  • Poor quality of life. Many people with moderate to severe IBS report poor quality of life. Research indicates that people with IBS miss three times as many days from work as do those without bowel symptoms.
  • Mood disorders. Experiencing the symptoms of IBS can lead to depression or anxiety. Depression and anxiety also can make IBS worse.
By Mayo Clinic Staff