Greater density of familial alcoholism, as indicated by the occurrence of the condition in multiple biological relatives beyond the parents, is also potentially important (Aston and Hill, 1990; Yuan et al., 1996). Such quantitative estimates of familial loading may be more sensitive indicators of alcoholism vulnerability than the presence or absence of the disorder in a parent (Hill et al., 2000). Milne and colleagues (2009) found that individuals with the highest family density of alcoholism were most likely to receive a diagnosis of alcoholism, to be diagnosed with alcoholism at multiple times, to report greater impairment due to their alcoholism, and to utilize treatment. Therefore, the occurrence of alcoholism in multiple biological relatives may identify a particularly potent and highly heritable form of the disorder. The most severe and chronic form of alcoholism (e.g., Type II or Type B alcoholism) is described as starting at a young age, as being coupled with externalizing behavior problems, and as reflecting a dense family history (Babor, 1996; Cloninger, 1987; Zucker, 1987). Unfortunately, the manner in which this inherited liability is expressed phenotypically prior
