and low levels of constraint loaded onto a single, highly heritable (h2 = 0.81) additive genetic factor (Krueger et al., 2002). Of note, there were no unique genetic influences on conduct disorder. Rather, the additive genetic influences on conduct disorder were completely overlapping with the higher-level externalizing genetic factor. Multivariate analyses of externalizing psychopathology in other population-based samples similarly find evidence that these disorders share a single, highly heritable genetic factor (Kendler et al., 2003; Young et al., 2000). Thus, the genetic influences on conduct disorder broadly predispose individuals to a range of disinhibitory behaviors, rather than conduct disorder in particular.
