Since the development of H. pylori-associated diseases is influenced by a complicated cross talk among
the bacteria, the infected host, and the environmental situation, the presence of H. pylori itself does not
explain fully pathogenesis.This is reflected by the fact that many people do not develop H. pylori
associated diseases, and that H. pylori negative gastric ulcer patients are often found. Hence other factors, such
as stress, diet, smoking, sanitation, and host genetic background might contribute to the pathogenesis of
Japan, found that the recurrence rate of gastric ulcers in patients infected with H. pylori was much higher
than that in patients in whom H. pylori had been eradicated. Hence we hypothesized that a synergic
relationship between H. pylori infection and psychological stress on ulcer formation might exist.