After fitting the univariate sex-limitation models for both CD and AAB considered individually, bivariate Cholesky models of CD and AAB were fit to the data to determine the extent to which the covariation between CD and AAB was due to genetic, shared environmental and non-shared environmental influences. Because the results of the univariate sex-limitation models of CD were suggestive of qualitative sex differences, bivariate models of CD and AAB were fitted for males and females separately. Thus, opposite-sex twins were not included in the bivariate analyses.
