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 a great deal of 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.
Sometimes people have persistent indigestion that is not related to any of these factors. This type of indigestion is called functional, or nonulcer, and is caused by a problem with how food moves through the digestive tract.