Fact Sheet: Irritable bowel syndrome

What is irritable bowel syndrome?

The bowel or intestine is a particularly complicated organ. It stretches out to a length of five metres with muscles, nerves and the immune system all working closely together. On one hand it is picking out nutrients for the body to use, while at the same time separating out toxins and protecting the body from illness.

One of the most common bowel problems is irritable bowel syndrome (IBS). Other names used to describe this are irritable colon, mucus colitis, spastic colon or spastic colitis, and nervous stomach. It involves abdominal pain, with constipation and/or diarrhoea.

IBS is not dangerous, but the symptoms can sometimes be severe. It can have a major impact on people's daily activities and cause distress or even depression. If you count in milder cases, the condition affects up to 2 out of every 10 women and up to 1 out of 10 men. It usually starts in people between 35 and 50 years of age.

What causes IBS?

The causes of IBS are not known. There are many theories. The possible causes range from dietary triggers through to problems with the functioning of the bowel's muscle action and psychological factors such as stress.

While the problems of IBS might start in the stomach and small bowel, it is usually the large bowel that is affected the most.



The large bowel or colon is where the last stage of food digestion happens. By this time, the food and drink we have had has been processed into a liquid. The muscles in the colon push this digested food steadily onwards. As it moves along, the water is absorbed from the digested food, and the indigestible parts get thicker until a stool (bowel motion) forms.

What are the symptoms?

Problems in this digestion process can lead to the typical symptoms of IBS. These include:

• Abdominal pain and cramps
• Bloating
• Flatulence (gas)
• Diarrhoea, with too much water still remaining in the stool
• Constipation, where the stool stays too long in the colon

If you have had abdominal pain plus diarrhoea and/or constipation, on and off for at least 12 weeks in the last year, it is possible that the problem is irritable bowel syndrome.

However, these symptoms can also be caused by other conditions, such as lactose intolerance (intolerance to milk products) or coeliac diease (intolerance to wheat). There are also some more serious bowel conditions that have these symptoms, such as the inflammatory bowel diseases called ulcerative colitis and Crohn's disease. A doctor can help rule out other causes for the symptoms.

What are the treatment options?

The symptoms of IBS improve by themselves over time for most people. There are also many possible options for treatment or symptom relief. But there is still no treatment that has been found to definitely help most people with IBS. Some people have only (or mostly) constipation, some only (or mostly) diarrhoea, and others have both problems at once. Since the problem is not the same for everyone, there is also no one treatment that works for most people.

This makes the choice of treatment for people with IBS something of an experiment. One of the choices is anti-cramping medications, called anti-spasmodics. These might be able to help the bowel muscles relax and so help relieve cramps.

Further options might be able to prevent constipation and avoid some of the triggers for IBS. But there is not yet enough evidence to show whether or not they are likely to help. These include:

• Fibre supplements and so-called bulking agents
• Avoiding emotional stress
• Probiotic dairy products, such as yoghurt
• Complementary therapies like peppermint oil
• Exercise

There are some other medications that can be used for IBS, but more evidence is needed to be sure about their effectiveness and adverse effects. This includes antidepressants. While these might help relieve IBS for some people, they can have serious adverse effects. They are not approved for use for IBS in some countries, including Germany.

It might help to observe what seems to trigger IBS symptoms for you personally. For example, is there something in your diet that makes it worse, which you could then avoid eating? Are your symptoms getting worse at times of stress? Can you find ways to reduce stress in your life?

© IQWiG (Institute for Quality and Efficiency in Health Care)