Most behavioral outcomes have some degree of genetic influence (Polderman et al., 2015), and conduct disorder is no exception. Conduct and related externalizing disorders (e.g., substance use and abuse) are among the most active areas of behavioral genetic research. In view of this, there are already several excellent reviews of the heritability of conduct disorder and broadband antisocial behavior (Burt, 2009; INSERM Collective Expertise Centre, 2005; Polderman et al., 2015; Rhee and Waldman, 2002). We provide highlights from this literature, where samples of twins are often used to estimate heritability. Twin studies permit the partitioning of latent genetic and environmental influences via comparison of the phenotypic correlations of monozygotic (MZ) and dizygotic (DZ) twin pairs. Additive genetic, shared environmental, and non-shared environmental influences can be estimated owing to the fact that both types of twins are exposed to the same rearing environment, but that MZ twins share all of their genetic variation, while DZ twins share half of their genetic variation, on average. Shared environmental influences refer to experiences or events that both twins experience that make them more similar
