causes for gastritis:
1)HP:Helicobacter pylori is one of the major causative factors ;
2)NSAID: Taking nonsteroidal anti-inflammatory drugs (NSAID) and aspirin can increase the risk of getting peptic ulcer disease by four times when compared to non-users.
3)Stress:Stress due to serious health problems such as those requiring treatment in an intensive care unit is well described as a cause of gastritis.
Dietary factors such as spice consumption, were hypothesized to cause ulcers until late in the 20th century, but have been shown to be of relatively minor importance. Caffeine and coffee, also commonly thought to cause or exacerbate ulcers, appear to have little effect.
Other causes of peptic ulcer disease includes: gastric ischaemia, drugs, metabolic disturbances, cytomegalovirus (CMV), upper abdominal radiotherapy, Crohn's disease, and vasculitis
It is still unclear if smoking does increase the risk of gastritis.