Publication
Intelligence in DSM‐IV combined type attention‐deficit/hyperactivity disorder is not predicted by either dopamine receptor/transporter genes or other previously identified risk alleles for attention‐d
Publisher:
Wiley
Date:
19-11-2007
DOI:
10.1002/AJMG.B.30596
Abstract: A major goal of genetic studies of attention deficit hyperactivity disorder (ADHD) is to identify in idual characteristics that might help segregate the disorder's inherent heterogeneity. [Mill et al. (2006) Arch Ger Psychiatry 63:462-469] recently reported a potentially important association between two dopamine-related risk polymorphisms (DRD4 variable number tandem repeat (VNTR) in exon 3 and DAT1 VNTR in the 3' UTR) and lowered IQ in ADHD. The objective of the current study was to replicate the [Mill et al. (2006) Arch Ger Psychiatry 63:462-469] findings in a clinical s le and to extend the analysis to a large range of alternative SNP markers of putative ADHD risk alleles identified in a recent study [Brookes et al. (2006) Mol Genet 11:934-953]. Participants were 1081 children and adolescents with a research-confirmed combined type ADHD diagnosis and 1300 unaffected siblings who took part in the International Multi-centre ADHD Genetics (IMAGE) project. They were recruited from multiple settings from across Europe: Belgium, Britain, Germany, Ireland, Israel, Netherlands, Spain and Switzerland. The results were that ADHD was associated with reduced IQ. However, there was no association between the two dopamine-related risk polymorphisms and IQ in either the probands or their siblings. Furthermore, other selected genetic markers previously demonstrated to be associated with ADHD in this s le were not associated with IQ. This large scale study with a clinically ascertained and regorously diagnosed s le failed to replicate the association between genetic polymorphisms in the dopamine system and IQ in ADHD. We also observed no association of other SNPs with IQ in ADHD.