That peptic ulcers are most commonly caused by bacteria triggers an absolute denial macro in some people, I've noticed. I was fascinated when I learned that helicobacter pylor was found to be the primary cause of stomach ulcers, but it really seems to put some people off. I've had a conversation like this more than once:

"I'm so stressed at work I'm going to get an ulcer."

"Did you know that most stomach ulcers are actually caused by bacterial infection?"

"Stress causes ulcers."

"No, really; not too long ago a certain bacteria was shown to cause the majority of peptic ulcers."

"Well stress makes you more susceptible to the infection then."

"That could be, but I don't know how much evidence there is for that..."

"My grandfather had ulcers; they were caused by stress."

"I'm just saying the majority of stomach ulcers aren't..."

"But some are caused by stress."

"I think they're correlated, but maybe the people who have ulcers are more under more stress because their stomach is bleeding?"

"I don't think that's very likely."

sigh...