The test of enrichment for AD association signals was performed in a case-control sample of 1399 phenotyped subjects of European descent only who were selected from the COGA sample. Cases had a lifetime diagnosis of AD by DSM-IV criteria. Controls reported consuming alcohol but did not have a diagnosis of AD or alcohol abuse by any of the diagnostic criteria assessed by SSAGA, and did not meet diagnostic criteria for dependence on cocaine, marijuana, opioids, sedatives or stimulants. Controls could not share a known common ancestor with a case and were preferentially selected to be above the age of 25 years. Genotyping was completed using the Illumina Human 1 M DNA Analysis BeadChip at the Center for Inherited Disease Research. Additional details on the COGA GWAS sample can be found in Edenberg et al. (2010) and Yan et al. (2014) [108, 109].
