title: Commonalities in the classical, collapsibility and counterfactual concepts of confounding.
abstract: OBJECTIVE
  Three definitions of confounding are available in the epidemiologic literature, namely, the classical, collapsibility, and counterfactual. The classical and collapsibility definitions are intuitively appealing but, especially in the case of the latter, there are shortcomings. The more recent counterfactual definition overcomes these limitations but at the cost of increased abstraction. One of the aims of this article is to demonstrate that under certain conditions the three definitions of confounding have key features in common.
  
  
  CONCLUSIONS
  The counterfactual definition of confounding addresses the inherent shortcomings of the classical and collapsibility definitions, and forms the basis of innovative methods of data analysis.
authors.affiliation: Department of Psychiatry, Mackenzie Centre, University of Alberta, Edmonton, Alberta T6G 2B7, Canada. stephen.newman@ualberta.ca
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Newman
mesh_terms: D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D006801:Humans; D008962:Models, Theoretical; D009626:Terminology as Topic