U.S. Department of Health and Human Services

Symptoms and Causes of Irritable Bowel Syndrome

What are the symptoms of IBS?​​​

The most common symptoms of irritable bowel syndrome (IBS) include pain or discomfort in your abdomen and changes in how often you have bowel movements or how your stools look. The pain or discomfort of IBS may feel like cramping and have at least two of the following:
  • Your pain or discomfort improves after a bowel movement.
  • You notice a change in how often you have a bowel movement.
  • You notice a change in the way your stools look.

IBS is a chronic disorder, meaning it lasts a long time, often years. However, the symptoms may come and go. You may have IBS if:

  • You’ve had symptoms at least three times a month for the past 3 months.
  • Your symptoms first started at least 6 months ago.
People with IBS may have diarrhea, constipation, or both. Some people with IBS have only diarrhea or only constipation. Some people have symptoms of both or have diarrhea sometimes and constipation other times. People often have symptoms soon after eating a meal.

Other symptoms of IBS are

  • bloating
  • the feeling that you haven’t finished a bowel movement
  • whitish mucus in your stool
Women with IBS often have more symptoms during their menstrual periods.
 
While IBS can be painful, IBS doesn’t lead to other health problems or damage your gastrointestinal (GI) tract.
 

What causes IBS?

Doctors aren’t sure what causes IBS. Experts think that a combination of problems can lead to IBS.

Physical Problems

Brain-Gut Signal Problems

Signals between your brain and the nerves of your gut, or small and large intestines, control how your gut works. Problems with brain-gut signals may cause IBS symptoms.

GI Motility Problems

If you have IBS, you may not have normal motility in your colon. Slow motility can lead to constipation and fast motility can lead to diarrhea. Spasms can cause abdominal pain. If you have IBS, you may also experience hyperreactivity—a dramatic increase in bowel contractions when you feel stress or after you eat.

Pain Sensitivity

If you have IBS, the nerves in your gut may be extra sensitive, causing you to feel more pain or discomfort than normal when gas or stool is in your gut. Your brain may process pain signals from your bowel differently if you have IBS.

Infections

A bacterial infection in the GI tract may cause some people to develop IBS. Researchers don’t know why infections in the GI tract lead to IBS in some people and not others, although abnormalities of the GI tract lining and mental health problems may play a role.

Small Intestinal Bacterial Overgrowth

Normally, few bacteria live in your small intestine. Small intestinal bacterial overgrowth is an increase in the number or a change in the type of bacteria in your small intestine. These bacteria can produce extra gas and may also cause diarrhea and weight loss. Some experts think small intestinal bacterial overgrowth may lead to IBS. Research continues to explore a possible link between the two conditions.

Neurotransmitters (Body Chemicals)

People with IBS have altered levels of neurotransmitters—chemicals in the body that transmit nerve signals—and GI hormones. The role these chemicals play in IBS is unclear.
 
Younger women with IBS often have more symptoms during their menstrual periods. Post-menopausal women have fewer symptoms compared with women who are still menstruating. These findings suggest that reproductive hormones can worsen IBS problems.

Genetics

Whether IBS has a genetic cause, meaning it runs in families, is unclear. Studies have shown IBS is more common in people with family members who have a history of GI problems.

Food Sensitivity

Many people with IBS report that foods rich in carbohydrates, spicy or fatty foods, coffee, and alcohol trigger their symptoms. However, people with food sensitivity typically don’t have signs of a food allergy. Researchers think that poor absorption of sugars or bile acids may cause symptoms.

Mental Health Problems

Psychological, or mental health, problems such as panic disorder, anxiety, depression, and post-traumatic stress disorder are common in people with IBS. The link between mental health and IBS is unclear. GI disorders, including IBS, are sometimes present in people who have reported past physical or sexual abuse. Experts think people who have been abused tend to express psychological stress through physical symptoms.

If you have IBS, your colon may respond too much to even slight conflict or stress. Stress makes  your mind more aware of the sensations in your colon. IBS symptoms can also increase your stress level.​

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​February 23, 2015​​​​

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