Using a family-based sample from the Collaborative Study on the Genetics of Alcoholism (COGA), Edenberg et al. (2010) performed a GWAS which interrogated over 850,000 SNPs in European and African Americans for association with DSM-IV alcohol dependence (n = 1399) (Edenberg et al., 2010). Alcohol-dependent probands were ascertained through alcohol treatment programs at seven centers across the United States. Thus cases represent a population with more severe alcohol dependence. Control subjects (age greater than 25 years old) were drawn from the community across the seven centers and were required to have consumed alcohol but not to have a diagnosis of alcohol abuse, dependence or harmful use at any time in their lives. The selected controls also could not meet criteria for DSM-3R or DSM-4 diagnoses of abuse or dependence on cocaine, marijuana, opioids, sedatives, or stimulants. However, study exclusion based on a diagnosis of substance dependence was not a requirement for cases because of the significant co-morbidity between alcohol and substance dependence. Several analyses were performed with the European American case-control GWAS being the primary analysis. Although no genome-wide significant
