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Irritable Bowel Syndrome: Symptoms and Risk Factors

Irritable bowel syndrome (IBS) is characterized by chronic abdominal pain and altered bowel habits. It affects 10 to 15 percent of the U.S. population and represents up to 50 percent of all referrals to gastroenterologists.

The cause is unknown. To date, no physiologic or psychological cause has been identified. Investigation has centered on abnormal gastrointestinal action, hypersensitivity of the gastrointestinal nerves, microscopic inflammation, infection, carbohydrate or bile acid malabsorption, and emotional stress, but clinical studies thus far are inconclusive.


  • Abdominal pain is the predominant symptom.
  • Altered bowel habits are also often present. This may occur as diarrhea, constipation, or alternating diarrhea and constipation.
  • Other symptoms include bloating, incomplete evacuation, nausea, difficulty swallowing, reflux, and heartburn.
  • IBS may also be accompanied by painful menstrual cycles, sexual dysfunction, fibromyalgia, and urinary symptoms.

Risk Factors

  • About half of cases occur in individuals younger than 35.
  • Women are affected twice as often as men.


Irritable Bowel Syndrome: Diagnosis and Treatment >>