Role of dopamine transporter genotype and maternal prenatal smoking in childhood hyperactive-impulsive, inattentive, and oppositional behaviors

Objective To examine the joint effects of a dopamine transporter (DAT) polymorphism and maternal prenatal smoking on childhood hyperactivity-impulsivity and inattentiveness. Study design A cohort of 161 children was followed prospectively from age 6 months to 60 months. Primary outcomes were the DSM-IV hyperactive-impulsive and inattentive scales of the Conners' Parent Rating Scale Revised-Long Version (CPRS R:L). A secondary outcome was the oppositional scale. Predictors included DAT genotype and maternal report of prenatal smoking. Children homozygous for the 480-bp DAT allele (DAT +/+) were compared with all other children (DAT +/- or -/-). Results In multivariate analyses, children with both prenatal smoke exposure and the DAT +/+ genotype had significantly elevated hyperactive-impulsive scores (beta, 7.5; SE, 2.9; P <.01) compared with children with no smoke exposure and DAT +/- or -/-. Inattentive scores were not significantly elevated in this group, but oppositional scores were a full standard deviation higher. Neither prenatal smoke exposure alone nor DAT +/+ genotype alone was significantly associated with increased scores. Conclusions Child hyperactivity-impulsivity and oppositional behaviors were associated with a DAT polymorphism but only when the child also had exposure to maternal prenatal smoking. This study emphasizes the importance of incorporating.