Case-control and within-family tests for an association between conduct disorder and DAT1

Conduct disorder (CD) is characterized by a persistent pattern of violating age-appropriate norms and the rights of others, and is one of the most frequently diagnosed disorders among children. CD is moderately heritable, but we know of no reliable associations with specific genes. Evidence suggests that a variable number tandem repeat polymorphism of the dopamine transporter (DAT1) gene may be associated with externalizing behavior in children. To test for an association between the DAT1 gene and CD. Case-control analyses and a transmission disequilibrium test (TDT) were conducted. Cases were (n=210) adolescents enrolled in a Colorado treatment program for conduct and substance use problems. Controls included adolescents matched to the probands in the treatment program and their siblings (n=162). The TDT was conducted using case families in which DNA from both parents was available (95 trios). The case-control analysis of the full sample did not result in a significant association [chi2 (2,372)=0.13, P=0.94]. Cases with early-onset conduct problems had slightly more 10-repeat alleles than controls, although this difference was not significant [chi2 (2,264)=2.19, P=0.33, 9/10 odds ratio (OR)=1.58, 10/10 OR=2.14]. The TDT also did not result in a significant association [chi2(1)=0.12, P=0.94]. Results did not support an association between this polymorphism of the DAT1 gene and CD in adolescents.