Prediction of Heterogeneity in Intelligence and Adult Prognosis by Genetic Polymorphisms in the Dopamine System Among Children With Attention-Deficit/Hyperactivity Disorder

Abstract

The findings indicate that genetic information of this nature may prove useful for etiology-based psychiatric nosologies.

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

“…No significant association was seen both in the unadjusted model (Table 1) (children with ADHD from the clinical sample: P = 0.769; ADHD-I community sample: P = 0.992; sample of adults with ADHD: P = 0.147), and in the model adjusted for potential confounders (P = 0.648, P = 0.907 and P = 0.847, respectively from children with ADHD from the clinical sample, ADHD-I community sample and adults; data available upon request). Therefore, our results did not replicate previous findings from Mill et al 5 suggesting that DAT1 and DRD4 VNTR polymorphisms did not influence IQ variation in three independent samples of Brazilian subjects with ADHD. Although Mill et al 5 replicated their findings in two independent cohorts, their two ADHD samples were smaller than those investigated in Brazil.…”

“…Therefore, our results did not replicate previous findings from Mill et al 5 suggesting that DAT1 and DRD4 VNTR polymorphisms did not influence IQ variation in three independent samples of Brazilian subjects with ADHD. Although Mill et al 5 replicated their findings in two independent cohorts, their two ADHD samples were smaller than those investigated in Brazil. Thus, our negative results do not seem to be owing to lack of statistical power to replicate their findings.…”

“…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.…”

“…As it is well-established that replication is an important condition to accept a given hypothesis in psychiatric genetics, we decided to examine the hypothesis proposed by Mill et al 5 in three independent samples of Brazilian subjects with ADHD. The first two samples were composed by 242 referred children with ADHD recruited at the Child and Adolescent Psychiatric Division of the Hospital de Clínicas de Porto Alegre (HCPA), and 220 adults with ADHD recruited at the adult clinic in the same hospital.…”

Attention problems, inhibitory control, and intelligence index overlapping genetic factors: A study in 9-, 12-, and 18-year-old twins.

“…Mill et al (2006) tested whether the DRD4 seven-repeat allele and the DAT1 10-repeat allele were associated with variation in intelligence among children with ADHD. They found evidence for this association in two independent samples, from New Zealand and the United Kingdom.…”