Causes

Doctors are not clear what the causes of IBS are. There is a complex link between the brain and bowel, through the large network of nerves that control the movements of the bowel. Anxiety, for example, seems to speed up the bowel, which is why many people get diarrhoea before an exam or job interview. It may be that this sort of reaction is more common in IBS sufferers, or persists where there is no obvious anxiety. There are various factors that can increase the symptoms associated with IBS. These include:

• emotional stress
• diet, especially one high in calories and fat
• hormonal changes, especially in females at times of their period

Often though, they crop up out of the blue, for no obvious reason at all. Symptoms may start after a period of stress, or a bout of gastroenteritis (inflammation of the stomach and intestines).

Emotional stress: Attacks of IBS are frequently triggered by life changes, for example feeling overworked and undervalued, upsetting arguments, having your purse stolen or a car accident. People with IBS tend to react to the normal ups and downs of life with their bowels. Many people report that their IBS started for the first time after a particularly upsetting event, like for example a parent dying, becoming unemployed or the breakdown of a key relationship.
People with IBS also tend to have been more likely than other people to have suffered from a tense, unhappy and sometimes traumatic childhood. Sufferers have higher rates of depression than the general population.
Psychological factors have an enormous influence on this condition. Ongoing emotional tension is the commonest reason for bowel sensitivity in this condition.

Diet: If the gut is sensitive, anything that goes in it will give rise to symptoms. This is why so many patients with IBS report that their symptoms are caused by so many different foods. It's not the food as much as the sensitive gut that is at fault here. Of course some foods affect all of us more than others. We are all more likely to experience gut upset if we eat very hot spicy foods, and experience gassy symptoms if we eat a lot of fruit and fibre. Not surprisingly, patients with the sensitive gut of IBS get a lot more symptoms from these foods.
Sometimes food has a particular emotional significance, for example being forced to eat certain foods as a child or sitting down to traumatic family meals. Eating the same food will cause emotional upset which will cause areas of gut to go into spasm and become very sensitive and give rise to symptoms.