All participants provided informed consent. There were 1238 individuals who completed the SSAGA interview and met DSM-IV AD diagnosis, including 591 probands, 620 affected siblings, and 27 affected individuals from 10 complex families. Controls were recruited in the Northern Ireland from volunteers donating at the Northern Ireland Blood Transfusion Service (N=554) and in the Republic from the Garda Siochana (the national police force, N=38) and the Forsa Cosanta Aituil (the army reserve, N=34). Controls were screened and their samples excluded if they reported a history of heavy drinking or problem alcohol use. In the present case-control study design, we included 575 independent AD cases (399 probands and 176 sibs) that were drawn one each from the IASPSAD families and 530 controls, with high yield of high quality DNA for genotyping.
