Abstract
Previous studies have demonstrated that the __Msp__I and __Dra__I polymorphisms at the alphaβ2Aβadrenergic receptor gene (ADRA2A) are associated with ADHD. However, few studies have been designed to ascertain the association between the ADRA2A genotypes and the performance on neurocognitive measures in ADHD. The aims of this study were to examine the association of the ADRA2A __Msp__I and __Dra__I polymorphisms with ADHD in Korean subjects, and to determine the relationship between the genotypes of these two polymorphisms and the candidate endophenotypes, as measured by the continuous performance test (CPT). In a caseβcontrol study, we assessed 186 ADHD probands and 150 normal controls. One hundred eight trios were studied in a family based association analysis. The transmission disequilibrium test (TDT) analysis showed preferential transmission of the C allele of the __Dra__I polymorphism (Ο^2^β=β5.88, Pβ=β0.015). In the haplotype analyses, a trend of overβtransmission of haplotype C/C was observed (Ο^2^β=β3.80, Pβ=β0.051). The homozygous subjects for the C allele (C/C genotype) at the __Dra__I polymorphism showed a trend toward a higher mean Tβscore with respect to the response time variability profiles of the CPT than did those with the other genotypes (C/Tβ+βT/T genotypes; Pβ=β0.042). The homozygous subjects for the G allele (G/G genotype) at the __Msp__I polymorphism showed a tendency to have a lower mean Tβscore with respect to the response time variability profiles of the CPT (Pβ=β0.068). The results of this study provide important evidence for the involvement of the ADRA2A __Msp__I and __Dra__I polymorphisms in the etiology of ADHD in Korean subjects. In addition, our results provide evidence for the possible role of these two polymorphisms in ADHD symptom expression, such as increased response time variability. Β© 2008 WileyβLiss, Inc.