What Is Irritable Bowel Syndrome (IBS)?


Irritable bowel syndrome (IBS) is a health condition in which the large intestine is affected by a simultaneously occurring group of intestinal symptoms. IBS causes stomach discomfort or pain, diarrhea or constipation, and changes in stool consistency (thin, hard, soft or liquid stools). It affects an estimated 10 to 15 percent of Americans.

Irritable bowel syndrome is also known as spastic colitis, mucous colitis, irritable colon or spastic colon. Although bowel changes occur, the risk of colorectal cancer does not increase with IBS. It is uncommon for intestinal damage to occur with IBS; however, symptoms may significantly alter one's lifestyle.


There are four types of irritable bowel syndrome:

  • Irritable bowel syndrome with constipation (IBS-C)
  • Irritable bowel syndrome with diarrhea (IBS-D)
  • Irritable bowel syndrome with mixed patterns of constipation and diarrhea (IBS-M)
  • Irritable bowel syndrome that does not easily fit into the other categories (IBS-U)


The severity and duration of irritable bowel syndrome symptoms vary on an individual basis. Symptoms of IBS typically occur at least three days a month for at least three months or longer, and severity often fluctuates. Common symptoms of IBS include the following:

  • Abdominal cramping or pain (oftentimes in the lower half of the stomach, which worsens after eating)
  • Bloating (may be relieved after a bowel movement)
  • Excessive gas (may be relieved after a bowel movement)
  • Diarrhea
  • Constipation
  • Constipation alternating with diarrhea
  • Hard or loose stools (often pellet or flat ribbon type)
  • Mucus in the stool
  • Stomach protrusion

Although urinary problems and sexual dysfunction may be symptoms of irritable bowel syndrome, they are rare.

Oftentimes, irritable bowel syndrome causes episodes of both constipation and diarrhea. Stress, certain foods and fluctuating hormones can cause IBS symptoms to worsen. The majority of people with IBS can control symptoms by managing lifestyle, diet and stress. Medications and counseling are available treatments for severe cases of IBS.

Possible causes

The exact cause of irritable bowel syndrome is unknown; however, certain factors play a role in its development:

  • Inflammation in the intestines, due to an increased number of immune-system cells associated with diarrhea and pain
  • Changes in good gut bacteria (microflora)
  • Strong or weak muscle contractions in the intestinal wall that move food through the digestive tract
  • Bacterial overgrowth in the intestines
  • Abnormalities in the nerves of the digestive system, which cause the body to overreact to changes in the digestive process

Risk factors

While occasional symptoms of irritable bowel syndrome occur in many people, certain factors increase the risk of developing the condition:

  • Female gender
  • Estrogen therapy prior to or after menopause
  • People under the age of 50
  • Family history of IBS
  • Mental health issues, such as anxiety, depression, etc.
  • History of physical, sexual or emotional abuse
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