We interpret findings in the context of broad confidence intervals due to available sample size and consistency of point estimates. Among familial vulnerability factors, we observed some evidence of specificity in the association between parental disorder and class membership. Paternal illicit drug use disorder was associated with the AUD and SUD-CD class but not the AUD-MDD-ANX class. Paternal externalizing disorder was uniquely associated with the SUD-CD class. Maternal depression was markedly and significantly associated (OR=3.33) with the AUD-MDD-ANX class and less so with the AUD and SUD-CD class (ORs = 1.49, 1.54). Together this suggests some specific familial contributions to comorbid externalizing disorders and to internalizing disorders over and above those in common with SUD. This is somewhat consistent with classical twin designs demonstrating genetic contributions specific to depression, anxiety and to conduct disorder that are not overlapping with genetic influences on SUD (Fu et al., 2007; Kendler et al. 2003).
