• Sensation in the stomach or the first part of the small intestine (the duodenum) may be altered in some way - an 'irritable stomach'. About one in three people with non-ulcer dyspepsia also have irritable bowel syndrome and have additional symptoms of lower tummy (abdominal) pains, erratic bowel movements, etc. The cause of irritable bowel syndrome is not known.
• A delay in emptying the stomach contents into the duodenum may be a factor in some cases. The muscles in the stomach wall may not work as well as they should.
• Infection with a germ (bacterium) called Helicobacter pylori (commonly just called H. pylori) may cause some cases. This bacterium is found in the stomach in some people with non-ulcer dyspepsia. However, many people are carriers of this bacterium and it causes no symptoms in most people. The role of H. pylori is controversial in non-ulcer dyspepsia (although it is the main cause of duodenal and stomach ulcers). However, getting rid of H. pylori infection helps in some cases.