title: The case-only odds ratio as a causal parameter.
abstract: In the simplest case-only design, cases of a disease are cross-classified into a 2 x 2 table describing a genotype attribute and exposure to some environmental agent. In some instances, the genetic attribute has described inherited genes; in other instances, it has described mutations, for instance, damage to proto-oncogenes or tumor suppressor genes leading to cancer. Here, the population case-only odds ratio is written as a causal parameter in terms of potential outcomes with and without exposure to the agent. It is shown that the case-only odds ratio makes sense as a causal parameter with inherited genes, but its magnitude does not have a causal interpretation with mutations, although deviations from 1 do provide information. The difference is that the environmental agent certainly did not cause an individual to inherit particular genes, but it may have caused the mutation.
authors.affiliation: Department of Statistics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6302, USA. rosenbaum@stat.wharton.upenn.edu
authors.forename: Paul R
authors.initials: PR
authors.lastname: Rosenbaum
mesh_terms: D001699:Biometry; D003069:Coffee / Q000009:adverse effects; D004194:Disease / Q000209:etiology; D004777:Environment; D005796:Genes; D011905:Genes, ras; D006801:Humans; D009154:Mutation; D016017:Odds Ratio; D010190:Pancreatic Neoplasms / Q000209:etiology / Q000235:genetics; D011897:Random Allocation
chemical_list: D003069:Coffee