Family history information for the COGA GWAS sample was obtained for both cases and controls as a dichotomous “yes” / “no” variable for any existence of a family history of AD, as reported by the subject. The SAGE GWAS sample included a “yes” / “no” variable about history of AD in specifically the proband’s mother and father. The presence or absence of family history was used as a binary variable in order to reflect clinical scenarios in which an individual is asked whether or not she or he has a family history of alcohol dependence.
