Association of high reaction time variability with the 7-repeat allele absence appears to be the most consistent result and seems to be specific to ADHD .
Speed of processing , set-shifting and cognitive impulsiveness were less frequently investigated but seem to be altered in the 7-repeat allele carriers .
High reaction time variability seems to be the most replicated cognitive marker associated with the 10-repeat homozygosity .
BACKGROUND We review ed systematic ally the results of genetic studies investigating associations between putative susceptibility genes for attention-deficit hyperactivity disorder ( ADHD ) and neuropsychological traits relevant for this disorder .
Association and linkage of alpha-2A adrenergic receptor gene polymorphisms with childhood ADHD.
Attention-deficit hyperactivity disorder ( ADHD ) is a heritable disorder , prevalent from childhood through adulthood . Although the noradrenergic ( NA ) system is thought to mediate a portion of the pathophysiology of ADHD , genes in this pathway have not been investigated as frequently as those in the dopaminergic system . Previous association studies of one c and i date gene in the NA system , ADRA2A , showed inconsistent results with regard to an MspI polymorphism . In the current study , two nearby single-nucleotide polymorphisms , which define HhaI and DraI restriction fragment length polymorphisms , were also genotyped and were in significant linkage disequilibrium with the MspI RFLP . Transmission disequilibrium tests ( TDTs ) in a sample of 177 nuclear families showed significant association and linkage of the DraI polymorphism with the ADHD combined subtype ( P=0.03 ) , and the quantitative TDT showed association of this polymorphism with the inattentive ( P=0.003 ) and hyperactive-impulsive ( P=0.015 ) symptom dimensions . The haplotype that contained the less common allele of the DraI polymorphism likewise showed a strong relationship with the inattentive ( P=0.001 ) and hyperactive-impulsive ( P=0.004 ) symptom dimensions . This study supports the hypothesis that an allele of the ADRA2A gene is associated and linked with the ADHD combined subtype and suggests that the DraI polymorphism of ADRA2A is linked to a causative polymorphism
Association of high reaction time variability with the 7-repeat allele absence appears to be the most consistent result and seems to be specific to ADHD .
Speed of processing , set-shifting and cognitive impulsiveness were less frequently investigated but seem to be altered in the 7-repeat allele carriers .
High reaction time variability seems to be the most replicated cognitive marker associated with the 10-repeat homozygosity .
BACKGROUND We review ed systematic ally the results of genetic studies investigating associations between putative susceptibility genes for attention-deficit hyperactivity disorder ( ADHD ) and neuropsychological traits relevant for this disorder .