Having established an etiologically coherent internalizing factor, we examined whether there was overlap in the genetic and environmental influences on this factor and marital relationship quality. The MZ twin correlation for Internalizing was .37, more than the DZ correlation of .27 but still less than twice as much (see Table 1). This indicates that genetic influences are important in the variance of Internalizing, but also implicates shared environmental effects. We ran a bivariate decomposition (Cholesky) model for marital quality and internalizing. As shown in Table 2, the heritability (proportion of total variance due to genetic effects) of internalizing was 24%, while proportion of variance due to shared family environment was 13% and the amount attributable to non-shared environmental effects was 62%. The genetic correlation between Marital Quality and Internalizing was 1.00, indicating that the genetic contributions to Marital Quality perfectly overlap with the genetic influences on the Internalizing spectrum. (Shared environmental factors (C) are not a substantial contributor to the etiology of Marital Quality, so the rC correlations of 1.0 are not useful to interpret, as they represent correlations between
