Objective: Attention deficit hyperactivity disorder (ADHD) has been shown to be highly heritable, and recent molecular genetics studies have focused on candidate genes in the dopaminergic and noradrenergic systems. One recent study reported an association of an allele of the TaqI polymorphism located in the fifth intron of the gene for dopamine beta-hydroxylase (DBH). The authors' goal was to replicate this finding.
Method: The authors investigated the linkage of the alleles and haplotypes of three polymorphisms at the DBH locus in 117 nuclear families with ADHD.
Results: No significant evidence was found for linkage of the TaqI alleles or haplotypes in the 117 families. However, the authors observed some evidence for biased transmission of the same allele of the TaqI polymorphism, as previously reported.
Conclusions: These findings suggest that the gene for DBH should be investigated further.