Irritable bowel syndrome : main article

Irritable bowel syndrome (IBS) is best defined as a functional disorder, characterised by abdominal pain or discomfort and associated with abnormal defaecation. It is extremely common, with a worldwide prevalence of 10 - 15%. IBS is more common in women than in men and typically presents in the third or fourth decades of life. It rarely manifests over the age of 50. There is substantial overlap with other 'functional diseases' such as fibromyalgia, interstitial cystitis and non-ulcer dyspepsia.