What causes indigestion (dyspepsia)?

The digestive problems may have an identifiable cause, such as bacterial or viral infection, peptic ulcer, gallbladder, or liver disease. The bacteria Helicobacter pylori is often found in those individuals suffering from duodenal or gastric ulcers. Investigation of recurrent indigestion should rule out these possible causes. Often, there is no organic cause for the problem, in which case dyspepsia is classified as functional or nonulcer dyspepsia. There is evidence that functional dyspepsia may be related to abnormal motility of the upper gastrointestinal tract (a state known as dysmotility in which the esophagus, stomach, and upper intestine behave abnormally). These patients may respond to a group of drugs called prokinate agents. A review of eating habits (e.g. chewing with the mouth open, gulping food, or talking while chewing) may reveal a tendency to swallow air. This may contribute to feeling bloated, or to excessive belching. Smoking, caffeine, alcohol, or carbonated beverages may contribute to the discomfort. When there is sensitivity or allergy to certain food substances, eating those foods may cause gastrointestinal distress. Some medications are associated with indigestion. Stomach problems may also be a response to stress or emotional unrest.

A disease or an ulcer in the digestive tract might cause indigestion. However, for most people, it is the result of eating too much, eating too fast, eating high-fat foods, or eating during stressful situations. Indigestion is not caused by excess stomach acid. Swallowing excessive air when eating may increase the symptoms of belching and bloating which are often associated with indigestion. Some medications can also irritate the stomach lining and cause indigestion.

Being tired or stressed, smoking, or drinking too much alcohol or caffeinated beverages can cause indigestion or make it worse. These factors can also worsen underlying conditions that cause indigestion, such as hiatal hernias and gastroesophageal reflux disorder (GERD). Emotional stress or other psychological conditions may result in abdominal pain.

Helicobacter pylori (H. pylori) is a bacterium, which lives in the mucus layer of the stomach, that can cause irritation (gastritis). It is present in about half the population, often without causing any symptoms. However, a high percentage of people who suffer from a stomach ulcer are found to carry the bug and about 15% of people who carry the bug will go on to develop an ulcer. It is possible that a small proportion of people who are affected will develop stomach cancer.

Hiatus hernia occurs when part of the stomach slides through the diaphragm, which is the muscular sheet that separates the lungs and chest from the abdomen. Normally, the stomach is completely below the diaphragm (see diagram at the top of this factsheet). But in some people, part of the stomach slides up into the chest cavity. This is called a hiatus hernia, and it causes pain and heartburn. Hiatus hernia is most likely to occur in pregnant women and people who are overweight. If the symptoms are severe, it can be repaired by an operation.

Indigestion often accompanies an emotional upset, because the part of the nervous system involved in the so-called "fight-or-flight" response also affects the digestive tract. People diagnosed with anxiety or somatoform disorders frequently have problems with indigestion. Many people in the general population, however, will also experience heartburn, "butterflies in the stomach," or stomach cramps when they are in upsetting situations--such as school examinations, arguments with family members, crises in their workplace, and so on. Some people's digestive systems appear to react more intensely to emotional stress due to hypersensitive nerve endings in their intestinal tract.

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