For the GWAS, a sample of genetically unrelated cases and controls were selected from this pool of alcohol dependent and community ascertained families. Cases were all alcohol dependent by DSM-IV criteria at some time during their lives, and were selected from the families ascertained through alcohol dependent probands. The selected controls were required to have consumed alcohol but not to have a diagnosis of alcohol abuse, dependence or harmful use by any of the 4 diagnostic systems assessed in the SSAGA (Feighner, DSM-IIIR, DSM-IV, ICD-10) at any time in their lives. Because there might be shared genetic vulnerability with other substance use disorders, the selected controls also could not meet criteria for DSM-IIIR or DSM-IV diagnoses of abuse or dependence on cocaine, marijuana, opioids, sedatives, or stimulants. Controls were selected from both the community recruited families and the families recruited through an alcohol dependent proband, but could not share a known common ancestor with a case. Controls older than 25 years were preferentially selected, to increase the probability that they were beyond the peak age of risk for developing alcohol
