The risk factors for antisocial behavior differed for males and females in childhood but not adulthood, and genetic and environmental influences accounted for proportionally the same amount of variance in antisocial behavior for males and females both in childhood and adulthood. The types of risk factors for antisocial behavior that differ among the sexes may be genetic or environmental in origin. If there are sex-specific effects on antisocial behavior, they are likely to be small and may not account for much of the sex difference in the prevalence of antisocial behavior. Nonetheless, our findings of sex-specific effects on child antisocial behavior, combined with the replicated finding of a role for the X-linked MAOA gene in the etiology of antisocial behavior, suggest that molecular genetic studies aimed toward identifying the genes involved in the development of antisocial behavior may have some success if they focus on the X chromosome, or at minimum, conduct analyses separately by sex. Developing an understanding of the sources of the sex difference in the prevalence of antisocial behavior is likely to be quite complicated, involving research that takes into account the different developmental trajectories of antisocial behavior as well as the interplay between genes and environment.
