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No association between dopaminergic polymorphisms and intelligence variability in attention-deficit/hyperactivity disorder

Molecular Psychiatry volume 11, pages 1066–1067 (2006)Cite this article

Attention-deficit/hyperactivity disorder (ADHD) is one of the most common and heritable psychiatric disorders.1 Although it is characterized by core symptoms (inattention, hyperactivity and impulsivity), there is considerable heterogeneity in clinical features among individuals with ADHD.2 The use of endophenotypes has been suggested as an alternative approach to decrease this clinical heterogeneity in genetic investigations addressing ADHD.3, 4

Recently, Mill et al.5 demonstrated an association between the two most investigated polymorphisms in ADHD, the 40 bp variable number of tandem repeats (VNTR) at the DAT1 gene and the 48 bp VNTR at the DRD4 gene, with intelligence variability among children with ADHD in two independent birth cohorts from Britain and New Zealand. In that study, children with ADHD diagnosis were assessed based on mother and teacher reports using respectively DSM-IV or DSM-III criteria for the Britain and New Zealand cohorts. These investigators defined genetic risk by the presence of at least one DRD4 seven repeat allele and/or by the presence of homozygous 10/10 DAT1 genotype. Children were scored 0 if they carried no genetic risk, 1 if they carried one genetic risk factor and 2 if they carried both risks. In the British cohort (n=171), children with one genetic risk scored 2.6 intelligence quotient (IQ) points lower than children with no genetic risk, and children with both genetic risks scored 8.2 IQ points lower than children with no risk (P=0.02). These results were replicated in the New Zealand Cohort (n=55) (P=0.03). In both samples, the association between number of genotypes at risk and IQ remained significant after controlling for number of symptoms of hyperactivity/impulsivity and inattention.

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Authors and Affiliations

  1. Department of Genetics, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil

    J P Genro, C H D Bau & M H Hutz

  2. Department of Morphological Sciences, Federal School of Medical Sciences of Porto Alegre, Porto Alegre, RS, Brazil

    T Roman

  3. Department of Psychiatry, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil

    C P Zeni, E H Grevet, M Schmitz, P B de Abreu & L A Rohde

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  1. J P Genro
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  2. T Roman
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  9. M H Hutz
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Correspondence to M H Hutz.

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Genro, J., Roman, T., Zeni, C. et al. No association between dopaminergic polymorphisms and intelligence variability in attention-deficit/hyperactivity disorder. Mol Psychiatry 11, 1066–1067 (2006). https://doi.org/10.1038/sj.mp.4001900

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