Table 3 provides a more detailed examination of the results for the genetic risk factors in our best-fit model. The heritability of the individual AD criteria ranged from 36% (for ‘desire to quit’) to 59% (for preoccupation). The two stem items were also substantially heritable. Table 3 also presents the percentages of the total heritability of each criterion attributable to each of the three genetic common factors. For the two stem items, and five of the seven criteria, one factor clearly provides the bulk of the heritable variance. For two of the criteria, the results are less clear. Interestingly, the preoccupation criterion has very similar contributions from the factor 1 (tolerance/excess drinking) and factor 2 (loss of control/social dysfunction), whereas the ‘activities given up’ criterion has only a moderately stronger contribution from factor 2 than from factor 3 (withdrawal/continued use).
