In previous chapters we saw evidence that males are more antisocial than females. In the next three chapters we ask if the aetiology of antisocial behaviour differs for males and females. This chapter takes a first look at this question by testing the hypothesis that males are more vulnerable than females to individual, familial, and environmental risk factors for antisocial behaviour. The basic premise is that biological sex or psychological gender serve either to exacerbate the influence of the risk factor or conversely to protect the individual from its influence.

Three types of research designs have been used to try to address the question of whether certain risk factors have a greater influence on the development of antisocial behaviour in males versus females. One approach is to use behavioural genetic designs to examine whether there are any sex differences in the genetic and environmental aetiology of antisocial behaviour. The available evidence suggests that estimates are more similar than different among males and females for genetic and environmental liability for externalizing behaviour problems (Gjone, Stevenson, and Sundet, 1996; Gjone et al., 1996), conduct problems (Cadoret and Cain, 1980; Cadoret et al., 1995; Slutske et al., 1997), and crime (Baker et al., 1989; Gottesman, Goldsmith, and Carey, 1997). Two studies that have found sex differences in the magnitude of genetic and environmental influences on antisocial behaviour reached opposite conclusions (Eley et al., 1999; Silberg et al., 1994).