Genetic and environmental influences on AA and AD, including significant qualitative genetic sex differences, have been previously reported for this sample: Prescott and colleagues (Prescott et al., 1999) found evidence of non-overlapping genetic influences on AA and AD, and reported heritability estimates of 51%-66% across diagnoses and sexes. The analyses reported here are extensions of these previous findings: bivariate models were used to assess the significance of genetic factors influencing AUD but not AA/AD (represented by the dashed lines in Figure 1). Based on the prior findings (Prescott et al., 1999), the model allowed for qualitative genetic differences across the sexes. Model fitting was limited to testing the significance of common environmental effects (in keeping with Prescott et al., 1999) and the significance of genetic influences loading onto AUD but not onto AA/AD. The phenotypes used for these analyses were the AUD phenotype described above, and a variable that combines the AA and AD diagnoses. For the DSM-IV phenotype, any individuals who met diagnostic criteria for either AA or AD was coded as “1”; all others were coded as “0”;
