Third, we found substantial quantitative differences in the genetic and environmental parameter estimates of our externalizing spectrum in males and females. Of three prior broadly comparable studies, one (Kendler et al. 2011) did not explore quantitative sex effects while one study (Kendler and Myers 2013) found and the other did not find (Hicks et al. 2004) evidence for such an effect. Our large sample probably gave us substantial power to detect some interesting differences in the structure of the externalizing syndrome in males and females.
