Causal Inference in Retrospective Studies

The problem of drawing causal inferences from retrospective case-control studies is considered. A model for causal inference in prospective studies is reviewed and then applied to retrospective studies. The limitations of case-control studies are formulated in terms of the level of causally relevant parameters that can be estimated in such studies. An example using data from a large retrospective study of coffee-drinking and myocardial infarctions is used to illustrate the ideas of the article.