title: Observational evidence.
authors.affiliation: Division of Preventive Medicine, Harvard Medical School, Brigham and Women's Hospital, Boston, MA 02215-1204.
authors.forename: C H
authors.initials: CH
authors.lastname: Hennekens
authors.forename: J E
authors.initials: JE
authors.lastname: Buring
mesh_terms: D000818:Animals; D015982:Bias; D016022:Case-Control Studies; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D006801:Humans; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D012107:Research Design; D012307:Risk Factors; D016896:Treatment Outcome