DOPAMINE D4 RECEPTOR GENE POLYMORPHISM IS ASSOCIATED WITH ATTENTION-DEFICIT HYPERACTIVITY DISORDER

Dopamine is believed to play a major role in the manifestation of atte ntion deficit hyperactivity disorder (ADHD), which affects 3-6% of sch ool-age children and shows evidence of familiarity, The dopamine D4 re ceptor, which is preferentially distributed in cortical and limbic reg ions of the brain, is currently of major interest because of the high degree of functionally relevant variability in its gene (DRD4), and th e association of this gene with Novelty Seeking behavior, We examined the variability in the length of a region of DRD4 that contains a 48-b p repeat sequence in children with ADHD and controls matched for ethni city, ADHD children differed from controls in that the 7-fold repeat f orm of DRD4 occurred significantly more frequently than in the control sample, This form of the receptor has previously been shown to mediat e a blunted intracellular response to dopamine. Although ADHD is likel y to be multifactorial in its etiology and its heritability is likely to be polygenetic, the present findings suggest that polymorphic varia tion in the gene encoding the D4 dopamine receptor may be a contributi ng factor in the expression of symptoms associated with ADHD.