There is strong evidence of familial aggregation of AD and related traits. Numerous studies have shown that first degree relatives of alcoholics are two to seven times more likely to develop problems with alcohol at some time in their lives, than individuals without a family history of AD (Grant, 1998; Nurnberger et al., 2004; Reich et al., 1998). Family history of alcoholism might be an indicator of shared or common environmental factors, genetic influences, or a combination of both (Grant, 1998). Familiality of alcoholism is also associated with age at onset and severity of AD (Limosin et al., 2001).
