How can stress lead to chronic duodenal ulcers?

Very complex: The pathophysiology of stress-related ulcers is complex. Infection with h pylori is by now a well-known factor. Chronic stress can lead to changes in GI blood flow that allows breakdown and disrepair of protective barriers to stomach & intestinal lining -- resulting in tiny micro-erosions that proceed to larger ones (ulcers). Patients in the ICU often experience such changes also.