Table 3 summarizes variance component estimates for the quadrivariate genetic model, with genetic and environmental correlations between the variables summarized in Table 4. Major genetic conclusions are: (a) moderate heritability of AD symptom count (39%), with a genetic correlation with the temporal clustering variable approaching unity (rG=0.99); (b) high heritability of heaviness of consumption (50%), with a high genetic correlation with AD symptom count (rG=0.97); (c) high heritability of alcohol abuse (51% in non-AD individuals), with a high genetic correlation with AD symptoms (rG=0.96). Non-shared environmental correlations were intermediate in magnitude and, for conditional phenotypes, had broad confidence intervals. Shared environmental parameters were all non-significant. As shown in Table 5, the genetic correlations between the consumption factor score (set to missing for those with 3 or more AD symptoms) and individual DSM-IV AD symptoms ranged from 0.67 to 0.95, with complete genetic overlap a possibility for 6 of the 7 symptoms.
