ASPD and ASPD/CD were both found to be highly heritable in this American Indian population. There have been few studies of the heritability of the diagnosis of ASPD published previously. In one study, of the Vietnam Era Twin Sample, a heritability of 0.67 was found, similar to the estimated heritability of that trait in this population of American Indians (0.76) (Slutske, 2001). However, significant evidence for a heritable component for CD was not found in this American Indian population. A number of authors have suggested that genetic influences may impact antisocial behaviors in adulthood more than during childhood or adolescence (Cloninger and Gottesman, 1987). Lyons et al., (1995) reported a lower heritability estimate for a CD symptoms scale than a scale of adult antisocial behavior symptoms. Additionally, Hesselbrock and Hesselbrock (1994) noted that among patients being treated for alcohol dependence, associations of the clinical characteristics of alcohol dependence with CD were much less striking that those with ASPD. Thus, it appears that in some populations that a history of childhood conduct symptoms without subsequent adult antisocial symptomatology may be less
