Irritable bowel syndrome (IBS) is a common disorder that affects the large intestine (colon). Irritable bowel syndrome commonly causes cramping, abdominal pain, bloating, gas, diarrhea and constipation. IBS is a chronic condition that you will need to manage long term.
Even though signs and symptoms are uncomfortable, IBS — unlike ulcerative colitis and Crohn’s disease, which are forms of inflammatory bowel disease — doesn’t cause changes in bowel tissue or increase your risk of colorectal cancer.
Only a small number of people with irritable bowel syndrome have severe signs and symptoms. Some people can control their symptoms by managing diet, lifestyle and stress. Others will need medication and counseling.
The signs and symptoms of irritable bowel syndrome can vary widely from person to person and often resemble those of other diseases. Among the most common are:
- Abdominal pain or cramping
- A bloated feeling
- Diarrhea or constipation — sometimes alternating bouts of constipation and diarrhea
- Mucus in the stool
For most people, IBS is a chronic condition, although there will likely be times when the signs and symptoms are worse and times when they improve or even disappear completely.
It’s not known exactly what causes irritable bowel syndrome, but a variety of factors play a role. The walls of the intestines are lined with layers of muscle that contract and relax in a coordinated rhythm as they move food from your stomach through your intestinal tract to your rectum. If you have irritable bowel syndrome, the contractions may be stronger and last longer than normal, causing gas, bloating and diarrhea. Or the opposite may occur, with weak intestinal contractions slowing food passage and leading to hard, dry stools.
Abnormalities in your gastrointestinal nervous system also may play a role, causing you to experience greater than normal discomfort when your abdomen stretches from gas or stool. Poorly coordinated signals between the brain and the intestines can make your body overreact to the changes that normally occur in the digestive process. This overreaction can cause pain, diarrhea or constipation.
Many people have occasional signs and symptoms of irritable bowel syndrome, but you’re more likely to have IBS if you:
- Are young. IBS tends to occur in people under age 45.
- Are female. Overall, about twice as many women as men have the condition.
- Have a family history of IBS. Studies suggest that people who have a family member with IBS may be at increased risk of the condition.
- Have a mental health problem. Anxiety, depression, a personality disorder and a history of childhood sexual abuse are risk factors. For women, domestic abuse may be a risk factor as well.
The influence of family history on IBS risk may be related to genes, shared factors in a family’s environment or both.