Genotype–environment interaction in antisocial behaviour

The question of nature versus nurture in most forms of human behaviour has been raised many times but has never been solved to the mutual satisfaction of the parties concerned. The current controversy over the importance of genes and the environment in determining IQ is a case in point. In the area of psychopathology, research using adoptees over the past fifteen years has mainly focused upon demonstrating a genetic factor in a variety of psychiatric conditions: schizophrenia (Heston, 1966;Ketyefa/. 1968; Rosenthale/a/. 1968; Wenderefa/. 1968;Karlsson, 1966), unipolar and bipolar affective disorders (Mendlewicz & Rainer, 1977; Cadoret, 1978), alcoholism (Bohman, 1978; Goodwin et al. 1973, 1974; Cadoret et al. 1980), antisocial personality (Crowe, 1974; Schulsinger, 1972), and antisocial forms of behaviour such as criminality (Hutchings & Mednick, 1977). Most of these studies have succeeded in showing the importance of a genetic factor in these varied conditions. It is noteworthy that this recent injection of genetic factors into aetiologies of conditions that previously had been felt to be largely the product of environment has not generated the heat of the IQ nature-nurture controversy. In part, this might reflect such factors as the lack of implication of major racial differences in the 'genetic factors' (the adoption studies cited above deal almost entirely with Caucasian samples and race is not mentioned as a confounding variable), or it could reflect the relatively small number of inheritance studies in psychopathology compared with IQ. Or again, no recent adoption studies have suggested specific social action (or even implied it) to alter the genetic factor. However, the potential for great nature versus nurture controversy exists, especially for those psychopathological conditions which are strongly associated with social or environmental factors. One such category of conditions is antisocial personality, which in numerous studies has been associated with (lower) social class, disturbed family background (Robins, 1966; West & Farrington, 1977; Glueck & Glueck, 1968) and, more important, potentially controllable environmental factors, such as type of schools attended (Rutter et al. 1979). Social manipulation is already practised by society (as in removing children from certain abusive or neglectful parents). In considering possible social action aimed at reducing the incidence of antisocial personality or antisocial behaviour, genetic and environmental effects would have to be carefully distinguished. More important would be evidence of genotype-environment interaction the potentiation of genetic effects in the presence of certain environments, or other interactions such as environments which' protect' against the effects of a given genotype. Obviously, genotype-environment interactions would be of practical importance in suggesting more specific and individualized changes. The remainder of this paper will review some recent evidence for the importance of genetic and environmental factors and their interaction in antisocial behaviour. In some of the adoption studies cited above, environmental factors have been investigated because certain adoptee experimental designs lend themselves to an assessment of the effect of environment. Negative results have been reported in alcoholism (Goodwin et al. 1973, 1974; Cadoret et al. 1980) and schizophrenia (Wender et al. 1968). However, more positive evidence of the importance of environmental factors has come out of adoption studies of antisocial personality or antisocial behaviour such as criminality. An early report of environmental influences on adoptee criminal behaviour came from Hutchings' analysis of data correlating registered criminality in adoptees with registered criminality in biological and adoptive parents (Hutchings, 1972). A multiple regression