Causes of Irritable bowel syndrome

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The precise cause of irritable bowel syndrome is unknown. The condition often begins during a period of emotional stress and symptoms worsen in stressful situations.

Up to 60 per cent of people with the syndrome have psychological symptoms such as anxiety and depression. The disorder sometimes develops after a gastrointestinal infection. An increased sensitivity or intolerance to certain foods, may also contribute.

It may result from exaggerated contractions of the muscles in the intestinal walls. These abnormal contractions can be tested by placing pressure-sensing devices in the colon. The colon muscle of a person with IBS begins to spasm after only mild stimulation and is more sensitive and reactive than usual.

The chemical transmitter that mediates the change to pressures within the bowel has been identified as serotonin, a chemical found in the brain as well as in the bowel. Ninety-five per cent of serotonin is found in the bowel. In the bowel, serotonin is mainly concerned with the contraction of the smooth muscle in the bowel wall. The exact mechanism is not known but serotonin receptors are thought not to function properly in IBS.