title: The DRD2 TaqI polymorphism and symptoms of attention deficit hyperactivity disorder.
abstract: The relationship of the DRD2 TaqI-A1 allele to hyperactive/impulsive and inattentive symptoms of attention deficit hyperactivity disorder (ADHD) in children and adolescents was examined in a sample of clinic-referred children and their siblings, and control children and their siblings (n = 236). The contribution of genetic dominance and additivity to mean differences among the A2A2, A1A2, and A1A1 genotypes was estimated using structural equation modeling. The effect of genetic additivity was statistically significant for both traits in an analysis of all children. The heritability from the DRD2 locus was estimated at 4.27% for hyperactive-impulsive symptoms and 2.12% for inattentive symptoms. Children with the A2A2 genotype had the highest mean level of symptoms. To control for any possible effects of population stratification, this analysis was repeated with parental genotypes as controls. In this smaller sample, although the direction of the effect was the same as that in the whole sample, the genotypic differences failed to reach conventional significance levels and the effect sizes were smaller (h2 = 1.62% and 0.79%, respectively). Furthermore, a genotype relative risk test of children who had questionnaire-based diagnoses of ADHD also failed to yield evidence of either association or linkage. Given that the A1 allele was expected to be the high risk allele, and that results were non-significant in tests that controlled for population heterogeneity, we doubt that this DRD2 polymorphism influences symptoms of ADHD in childhood.
authors.affiliation: Graduate Program in Genetics, Division of Family Studies, Campus Box 210033, University of Arizona, Tucson, AZ 85721, USA. dcr091@ag.arizona.edu
authors.forename: D C
authors.initials: DC
authors.lastname: Rowe
authors.forename: E J
authors.initials: EJ
authors.lastname: Van den Oord
authors.forename: C
authors.initials: C
authors.lastname: Stever
authors.forename: L N
authors.initials: LN
authors.lastname: Giedinghagen
authors.forename: J M
authors.initials: JM
authors.lastname: Gard
authors.forename: H H
authors.initials: HH
authors.lastname: Cleveland
authors.forename: M
authors.initials: M
authors.lastname: Gilson
authors.forename: S T
authors.initials: ST
authors.lastname: Terris
authors.forename: J H
authors.initials: JH
authors.lastname: Mohr
authors.forename: S
authors.initials: S
authors.lastname: Sherman
authors.forename: A
authors.initials: A
authors.lastname: Abramowitz
authors.forename: I D
authors.initials: ID
authors.lastname: Waldman
mesh_terms: D000293:Adolescent; D000328:Adult; D000483:Alleles; D001289:Attention Deficit Disorder with Hyperactivity / Q000235:genetics*; D001923:Brain Chemistry / Q000235:genetics; D002648:Child; D005192:Family Health; D005260:Female; D008040:Genetic Linkage; D005838:Genotype; D006801:Humans; D008297:Male; D011110:Polymorphism, Genetic; D017448:Receptors, Dopamine D2 / Q000235:genetics*; D019914:Taq Polymerase
chemical_list: D017448:Receptors, Dopamine D2; D019914:Taq Polymerase