This is more classical and common. The ulcer penetrates deep into the mucosa. These are not known for sure. The number of acid-secreting cells is high, with greater outpouring of acid. Excessive acid flow is consequential, in comparison to gastric ulcer where defective mucosal resistance is the cause.
Genetic factors appear to be important.
Alcohol and cigarettes are potent causative and aggravating factors. Stress produces and aggravates duodenal ulcer in any situation. Of this there is no doubt. All patients experience increase in pain with stress. The classic symptom is pain in the epigastric area present two to three hours after a meal.