The latest research sheds some light on the problem.
A number of theories aim to explain the disease in terms of physiological disorder.
These include possibilities such as smooth muscle abnormalities, altered small intestinal mobility, or a sensory condition causing normal mobility of the gut to feel strange and abnormal to a person.
However, no real evidence has been found to support any of these explanations.
It is in fact often the case that IBS sufferers are thought of as hypochondriacs without any real problem, and doctors who hold this belief tend to almost disregard their patients' gastrointestinal complaints.
It is possible that an overgrowth of bacteria is what causes irritable bowel syndrome.
The surge of bacteria would be present in the small intestine, as one researcher publishing in the Journal of the American Medical Association has proposed.
The proposal suggested that ordinary bacteria normally found in the large intestine may end up in the small intestine giving rise to the characteristic symptoms of IBS; uncomfortable bloating and gas and a change in bowel movements, together with muscle and joint pain, chronic fatigue and headaches which are sometimes found in sufferers.
There may be 100 trillion bacteria in the gut, but they are usually scarce in the small intestine, so an increase in bacteria here may account for the symptoms of IBS.
Another more common theory is that IBS is a stress-related disease.
It is often suggested that stress, anxiety and depression cause IBS, but thinking is now more along the lines that these psychological maladies only exacerbate the symptoms rather than bring them on.
Research has found the colon muscle of someone with IBS is more sensitive than that of a non-sufferer, which means that IBS sufferers have strong reactions to stimuli that would not affect others.
It is also suggested that hormones may influence symptoms, as women generally have more symptoms of IBS when menstruating.
A third possible cause of IBS is food intolerance.
Although caffeine and alcohol are generally found to aggravate IBS, different individuals may find they have 'trigger' foods which vary widely.
Sometimes this can be found out by trial and error in diet, but it is only possible to confirm food intolerance by blood testing for antibodies.
Once the foods are identified by the test, they can be cut out of the diet, leading to an improvement in IBS symptoms.
It is even the case that after a time, the foods which were previously a problem can be phased back into the diet as the immune system appears to reset itself in the interim.
Food intolerance testing kits are available from some pharmacies to make it easier to identify problem foods that may provoke the symptoms of IBS.
Copyright 2006 David McEvoy