Irritable bowel syndrome (IBS) is a common disorder that affects the stomach and intestines, also called the gastrointestinal tract. Symptoms include cramping, abdominal pain, bloating, gas, and diarrhea or constipation, or both. IBS is a chronic condition that you'll need to manage long term.
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 medication and counseling.
IBS doesn't cause changes in bowel tissue or increase your risk of colorectal cancer.
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Symptoms of IBS vary but are usually present for a long time. The most common include:
- Abdominal pain, cramping or bloating that is related to passing a bowel movement
- Changes in appearance of bowel movement
- Changes in how often you are having a bowel movement
Other symptoms that are often related include sensation of incomplete evacuation and increased gas or mucus in the stool.
Video: How irritable bowel syndrome affects you
IBS is a functional disorder. Even though the digestive tract looks normal, it doesn't function as it should. Muscles in the intestines move food from the stomach to the rectum. Normally, they contract and relax in a gentle rhythm that moves the food along in a fairly predictable schedule. But with some people, the muscles in the intestines spasm. That means the contractions are longer and stronger than normal. Those spasms are painful. They also disrupt the movement of food through the intestines. If they slow it down, you become constipated. If they cause it to move through too quickly, you get diarrhea. It's not unusual for people to alternate between the two. Another cause of discomfort for people with IBS results from oversensitive nerve endings in the digestive tract. Small bubbles of gas that wouldn't bother most people might be quite painful for you. Your heightened sensitivity can also lead to swelling and bloating.
When to see a doctor
See your health care provider if you have a persistent change in bowel habits or other symptoms of IBS. They may indicate 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 a bowel movement
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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 your 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 your digestive system may cause discomfort when your abdomen stretches from gas or stool. Poorly coordinated signals between the brain and the intestines can cause your 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 might also be associated with a surplus of bacteria in the intestines (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 reside 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.
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.
Many people have occasional symptoms of IBS. But you're more likely to have the syndrome if you:
- Are young. IBS occurs more frequently 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.
Chronic 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.
Irritable bowel syndrome care at Mayo Clinic
May 12, 2023
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