Next, we fit standard biometric models to derive more precise estimates of the genetic and environmental influences on each externalizing disorder and the general externalizing liability. Table 2 provides the sibling correlations and univariate ACE parameter estimates for each externalizing disorder. Each externalizing disorder exhibited moderate heritability (0.35 to 0.49) and nonshared environmental influences (0.38 to 0.48). Each disorder except alcohol dependence also exhibited significant shared environmental influences (0.09 to 0.26).
