Sex differences in the etiology of psychopathic traits in youth

Few studies have examined the etiology of psychopathic traits in youth, and even fewer have tested whether the genetic and environmental influences underlying these traits differ for boys and girls. We tested for sex differences in the etiology of 3 trait dimensions-impulsivity, narcissism, and callous-unemotionality (CU)-previously found to underlie youth psychopathy in our sample. Using biometric modeling we tested whether constraining the genetic and environmental influences for each dimension across sex reduced model fit. We also tested for qualitative sex differences in the influences underlying these dimensions by allowing the genetic and environmental correlations between opposite sex dizygotic twins to be less than their respective values in same-sex dizygotic twins. Although the magnitudes of the genetic and environmental influences underlying the CU and narcissistic trait dimensions did not differ for boys and girls, nonshared environmental influences contributed significantly greater variance to impulsive traits in boys. No qualitative sex differences were found in the influences underlying any of the 3 trait dimensions, suggesting that the same genes and environments contribute to these psychopathic traits in males and females.