title: Observational studies of treatment effectiveness: some cautions.
authors.forename: Andreas
authors.initials: A
authors.lastname: Laupacis
authors.forename: Muhammad
authors.initials: M
authors.lastname: Mamdani
mesh_terms: D003327:Coronary Disease / Q000401:mortality / Q000517:prevention & control*; D017052:Hospital Mortality; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000627:therapeutic use*; D019370:Observation; D055502:Secondary Prevention; D015983:Selection Bias; D016896:Treatment Outcome
chemical_list: D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors