From the outset, the goal of the Collaborative Studies on the Genetics of Alcoholism (COGA) was to identify genes and genetic mechanisms that contribute to the risk for alcohol use disorder (AUD)* (see, 1. Overview in this issue for an overview of the COGA study). It has long been recognized that AUD runs in families. 1 , 2 Twin and family studies estimate that roughly half of the variation in AUD is attributable to genetic factors and 10% is attributable to familial environmental factors. 3 , 4 , 5 , 6 , 7 Thus the family‐based design has proven advantageous. 8
