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 .
The homozygosity for 10-repeat allele at dopamine transporter gene and dopamine transporter density in Korean children with attention deficit hyperactivity disorder: relating to treatment response to methylphenidate
The symptoms of attention deficit hyperactivity disorder ( ADHD ) can be treated with methylpheni date ( MPH ) , a potent blocker of dopamine transporter ( DAT ) . The homozygosity of the 10-repeat allele at the DAT gene ( DAT1 ) seems to be associated with a poor response to MPH in children with ADHD . In the present study , we investigated the association between DAT density using I-123-N-(3-iodopropen-2-yl)-2beta-carbomethoxy-3beta-(4-chlorophenyl)tropane [123I]IPT single photon emission computed tomography ( SPECT ) ] and the homozygosity for 10-repeat allele at DAT1 and response to MPH in Korean children with ADHD . Eleven drug-naive children with ADHD were included in the study and treated with MPH for about 8 weeks . After the genotyping and SPECT were performed , we compared DAT density between ADHD children with and without the homozygosity for 10-repeat allele at DAT1 and investigated the correlation between the homozygosity for 10-repeat allele and response to MPH .  ADHD children with 10/10 genotype ( n=7 ) had a significantly greater increase of the DAT density in basal ganglia than the children without 10/10 genotype ( n=4 ) . We found that while only 28.6 % ( 2/7 ) of the subject with 10/10 genotype showed good response to  MPH  treatment , 100 % ( 4/4 ) of the subjects without 10/10 genotype showed good response to  MPH treatment . Our findings support an association between homozygosity for 10-repeat allele at DAT1 and the DAT density assessed in vivo and correlation between the homozygosity for 10-repeat allele and poor response to MPH
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 .