Early studies reported that relatives of alcoholics were approximately at a three to four-fold increased risk for AUD (Goodwin, 1989), which then led to studies that aimed to determine if this increased risk for AUD seen in children of alcoholics was still evident even if the they were not raised by their biological parents in an alcoholic environment. In the early 1970s a well-powered study which included a large sample of half-siblings who were raised by their alcoholic biologic families or raised by foster families who were not alcoholic, concluded that adverse alcohol outcomes in offspring related more closely to alcoholism in a biological parent than compared to alcohol problems in foster families (Schuckit et al., 1972). At about the same time this report was made several large adoption studies from the United States, Denmark, and Sweden reported a threefold or greater increased risk for AUD in sons of alcoholics even when they were adopted as infants and raised by nonalcoholic families (Goodwin et al., 1973, 1977,1974). For example, Goodwin et al. (1973) studied the drinking history of 55 adopted-out
