Despite strong evidence for a considerable genetic component to CD, there have been relatively few studies aimed at identifying genetic variation that contributes to the risk for this disorder. Two genome-wide linkage scans have been conducted on retrospectively reported CD, using data from the Collaborative Study on the Genetics of Alcoholism (COGA)15 and the Irish Affected Sib Pair Study of Alcohol Dependence (IASPSAD).16 CD symptoms have also been analyzed in the context of linkage scans that focused on externalizing psychopathology more generally.17–19 A number of chromosomal regions have been implicated by these studies, although the reported LOD scores have generally been modest, and none has yet led to the subsequent identification of an associated gene in the region. In addition, there are a small number of candidate gene studies of CD, with largely negative or inconsistent results. Association has been reported between the short allele of 5HTTLPR and CD with aggressive symptoms among adolescents ascertained through a substance abuse treatment program.20 However, another study failed to detect an association between this polymorphism and externalizing behavior in a sample of high-risk
