a broad externalizing factor,22–25 whereas others model it as a separate, but correlated, factor.26–29 We tested five alternative confirmatory factor analytic models, including a common factor model and alternative parameterizations of a two-factor structure to capture the genetic covariance among externalizing phenotypes and SUDs (Figure 1A–E). We followed up these analyses with exploratory factor analysis to evaluate alternative, data-driven clusters of phenotypes. Finally, to further characterize the differentiability of the factors identified in our models, we estimated their genetic correlations with other relevant traits and quantified the degree of polygenic overlap between externalizing and SUDs.
