In contrast, higher rates of externalizing disorders and substance dependence have been reported in several studies of Native American communities and clinic samples [28-29]. Only one study has examined the evidence for shared genetic influences between these diagnostic categories in Native Americans [30]. In that study, antisocial personality disorder (0.76) and antisocial personality disorder/conduct disorder (0.56) were found to be highly heritable and co-morbid with drug and alcohol dependence. Additionally, suggestive evidence for linkage (LOD score > 2.0) was found on chromosomes 1q43, 3q27, 4q12, 14q31.3, 17q25.3, and 20p11.23. Each of these linkage peaks have been related to alcohol and other substance use phenotypes in studies of other ethnic groups, and the loci identified on chromosomes 1 and 3 have been related to conduct symptoms in other linkage studies using general population samples [31]. Again, these studies suggest that the regions of the genome that influence externalizing disorders and substance dependence in Native Americans are most likely similar to those found in the general population.
