What is irritable bowel syndrome (IBS)?
Irritable bowel syndrome is a functional gastrointestinal (GI) disorder, meaning it is a problem caused by changes in how the GI tract works. People with a functional GI disorder have frequent symptoms, but the GI tract does not become damaged. IBS is not a disease; it is a group of symptoms that occur together. The most common symptoms of IBS are abdominal pain or discomfort, often reported as cramping, along with diarrhea, constipation, or both. People with IBS have some improvement in their pain or discomfort with bowel movements.
What are the symptoms of IBS?
The symptoms of IBS include abdominal pain or discomfort and changes in bowel habits that occur at least 3 days a month.
To meet the definition of IBS, the pain or discomfort should be associated with two of the following three symptoms:
- Start with bowel movements that occur more or less often than usual
- Start with stool that appears looser and more watery or harder and more lumpy than usual
- Improve with a bowel movement
Other symptoms of IBS may include:
- Diarrhea: loose, watery stools three or more times a day and feeling urgency to have a bowel movement
- Constipation: hard, dry stools; three or fewer bowel movements in a week; or straining to have a bowel movement
- Feeling that a bowel movement is incomplete
- Passing mucus, a clear liquid made by the intestines that coats and protects tissues in the GI tract
- Abdominal bloating
- Symptoms may often occur after eating a meal
What causes IBS?
The causes of IBS are not well understood. It is believed that a combination of physical and mental health issues can lead to IBS. The possible causes of IBS include the following:
- Brain-gut signal problems. Signals between the brain and nerves of the small and large intestines, also called the gut, control how the intestines work. Problems with brain-gut signals may cause IBS symptoms, such as changes in bowel habits and pain or discomfort.
- GI motor problems. Normal motility, or movement, may not be present in the colon of a person who has IBS. Slow motility can lead to constipation and fast motility can lead to diarrhea. Spasms, or sudden strong muscle contractions that come and go, can cause abdominal pain. Some people with IBS also experience hyper-reactivity, which is an excessive increase in contractions of the bowel in response to stress or eating.
- Hypersensitivity. People with IBS have a lower pain threshold to stretching of the bowel caused by gas or stool compared with people who do not have IBS. The brain may process pain signals from the bowel differently in people with IBS.
- Mental health problems. Mental health, or psychological, problems such as panic disorder, anxiety, depression, and post-traumatic stress disorder are more common in people with IBS. The link between these disorders and development of IBS is unclear. It is believed that IBS is one type of physical manifestation from psychological stress or anxiety.
- Bacterial gastroenteritis. Some people who have bacterial gastroenteritis, an infection or irritation of the stomach and intestines caused by bacteria, develop post-infectious IBS. It is not known why gastroenteritis leads to IBS in some people and not others, though psychological issues and abnormalities of the lining of the GI tract may be factors.
- Small intestinal bacterial overgrowth (SIBO). Normally, few bacteria live in the small intestine. SIBO is an increase in the number of bacteria or a change in the type of bacteria in the small intestine. These bacteria can produce excess gas and may also cause diarrhea and weight loss. Some researchers believe that SIBO may lead to IBS, and some studies have shown antibiotics to be effective in treating IBS. However, more research is needed to show a link between SIBO and IBS.
- Body chemicals. People with IBS have altered levels of neurotransmitters, which are chemicals in the body that transmit nerve signals, and GI hormones, though the role these chemicals play in developing IBS is unclear. Younger women with IBS often have more symptoms during their menstrual periods. Post-menopausal women have fewer symptoms compared with women who are still menstruating. These findings suggest that reproductive hormones can worsen IBS problems.
- Genetics. Whether IBS has a genetic cause, meaning it runs in families, is unclear. Studies have shown that IBS is more common in people with family members who have a history of GI problems. However, the cause could be environmental or the result of heightened awareness of GI symptoms.
- Food sensitivity. Many people with IBS report that certain foods and beverages can cause symptoms, such as foods rich in carbohydrates, spicy or fatty foods, coffee, and alcohol. However, people with food sensitivity typically do not have clinical signs of food allergy. It is believed that symptoms may result from poor absorption of sugars or bile acids, which help break down fats and get rid of wastes in the body.
How is IBS diagnosed?
IBS is diagnosed when a person has abdominal pain or discomfort at least three times per month for the last 3 months without other disease or injury that could explain the pain. The pain or discomfort of IBS may occur with a change in stool frequency or consistency or may be relieved by a bowel movement.
IBS is often classified into four subtypes based on a person’s usual stool consistency. These subtypes are important because they affect the types of treatment that are most likely to improve the person’s symptoms.
The four subtypes of IBS include:
- IBS with constipation (IBS-C): hard or lumpy stools at least 25 percent of the time and loose or watery stools less than 25 percent of the time
- IBS with diarrhea (IBS-D): loose or watery stools at least 25 percent of the time and hard or lumpy stools less than 25 percent of the time
- Mixed IBS (IBS-M): hard or lumpy stools at least 25 percent of the time and loose or watery stools at least 25 percent of the time
- Unsubtyped IBS (IBS-U): hard or lumpy stools less than 25 percent of the time and loose or watery stools less than 25 percent of the time
How common is IBS and who is affected?
Irritable bowel syndrome is estimated to affect 3 to 20 percent of the population, with most studies ranging from 10 to 15 percent. However, less than one-third of people with the condition see a health care provider for diagnosis. IBS affects about twice as many women as men and is most often found in people younger than 45 years.
How is IBS treated?
Though there is no cure for IBS, the symptoms can be treated with a combination of the following:
- Changes in eating, diet, and nutrition
- Large meals can cause cramping and diarrhea, so eating smaller meals more often, or eating smaller portions, may help IBS symptoms.
- Eating meals that are low in fat and high in carbohydrates, such as pasta, rice, whole-grain breads and cereals, fruits, and vegetables, may help.
- Certain foods and drinks may cause IBS symptoms in some people
- High fat
- Dairy products
- Alcohol
- Caffeine
- Large amounts of artificial sweeteners
- foods that gas and bloating such as beans, cabbage and carbonated beverages
- Keeping a food diary is a good way to track which foods cause symptoms so they can be excluded from or reduced in the diet.
- Dietary fiber may lessen constipation in people with IBS, but it may not help with lowering pain. Fiber helps keep stool soft so it moves smoothly through the colon. The Academy of Nutrition and Dietetics recommends consuming 20 to 35 grams of fiber a day for adults. Fiber may cause gas and trigger symptoms in some people with IBS. Increasing fiber intake by 2 to 3 grams per day may help reduce the risk of increased gas and bloating.
- Medications used to treat IBS vary depending on the type of symptoms
- Probiotics are live microorganisms, usually bacteria, that are similar to microorganisms normally found in the GI tract. Studies have found that probiotics, specifically Bifidobacteria and certain probiotic combinations, improve symptoms of IBS when taken in large enough amounts. But more research is needed. Probiotics can be found in dietary supplements, such as capsules, tablets, and powders, and in some foods, such as yogurt.
- Treatment of mental health issues such as stress and anxiety. Talking with a therapist may reduce stress and improve IBS symptoms. Two types of talk therapy used to treat IBS are cognitive behavioral therapy and psychodynamic, or interpersonal, therapy. Cognitive behavioral therapy focuses on the person’s thoughts and actions. Psychodynamic therapy focuses on how emotions affect IBS symptoms. This type of therapy often involves relaxation and stress management techniques.
What other conditions are associated with IBS?
People with IBS often suffer from other GI and non-GI conditions.
GI conditions such as gastroesophageal reflux disease (GERD) and indigestion (dyspepsia) are more common in people with IBS than the general population. Please refer to the sections Acid Reflux (Gastroesophageal Reflux Disease) and Indigestion (Dyspepsia) for more information about these conditions.
Non-GI conditions often found in people with IBS include
- Chronic fatigue syndrome: a disorder that causes extreme fatigue, which is tiredness that lasts a long time and limits a person’s ability to do ordinary daily activities
- Chronic pelvic pain
- Temporomandibular joint disorders: problems or symptoms of the chewing muscles and joints that connect the lower jaw to the skull
- Depression
- Anxiety
- Somatoform disorders: chronic pain or other symptoms with no physical cause that are thought to be due to psychological problems
How does stress affect IBS?
Stress can stimulate colon spasms in people with IBS. The colon has many nerves that connect it to the brain. These nerves control the normal contractions of the colon and cause abdominal discomfort at stressful times. In people with IBS, the colon can be overly responsive to even slight conflict or stress. Stress makes the mind more aware of the sensations that arise in the colon. IBS symptoms can also increase a person’s stress level.
Some options for managing stress include:
- Participating in stress reduction and relaxation therapies such as meditation
- Counseling and support
- Taking part in regular exercise such as walking or yoga
- Minimizing stressful life situations as much as possible
- Getting enough sleep