Why do ulcers form and what are the main causes behind their development?

Ulcers form when the protective lining of the stomach or small intestine is damaged, allowing stomach acid to create a sore. The main causes behind their development are infection with the bacteria H. pylori, long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs), excessive alcohol consumption, and smoking. Stress and genetics can also play a role in ulcer formation.