Confounding by indication and past clinical trials.
Porta
M
M
D000897:Anti-Ulcer Agents / Q000009:adverse effects* / Q000627:therapeutic use; D002927:Cimetidine / Q000009:adverse effects* / Q000627:therapeutic use; D015986:Confounding Factors, Epidemiologic; D006801:Humans; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D013274:Stomach Neoplasms / Q000139:chemically induced* / Q000453:epidemiology*
D000897:Anti-Ulcer Agents; D002927:Cimetidine