COGA is one of the few family‐based genetic projects with a significant number of African Americans, who are greatly underrepresented in such studies, particularly those with family‐based designs. Indeed, COGA's African ancestry genetic data comprise a substantial proportion of the sample size for some of the first African ancestry GWAS of addiction‐related phenotypes. 91 , 94 , 106 Using novel admixture mapping methods, COGA identified a region on chromosome 4 that was genome‐wide significant for self‐rating of the effects of ethanol in individuals of African ancestry, implicating PPARGC1A, 91 which has been previously linked to alcohol consumption.
