OBJECTIVES: The objective was to make a contribution to deepening the knowledge of the etiopathogenesis of ADHD. DESIGN: In an association study design, an analysis of polymorphisms of selected genes was conducted in 119 hyperkinetic boys and a control group of boys, aged 7-13. Furthermore several psychologically determined subgroups were identified. A connection between psychological functions (endophenotypes) and genes were looked for. RESULTS: There was a statistically significant difference found in allelic and genotype frequencies of the TaqI A polymorphism of the DRD2 gene. The frequency of the allele A1 in hyperkinetic boys and the control subjects was 0.26 and 0.15, respectively (p<0.003). A statistically significant occurrence of atypical genotypes (8/10, 7/10 and 10/11) of the DAT1 gene was also found in hyperkinetic boys and a connection between the M235 polymorphism of the angiotensinogene gene and the positive family history of psychiatric illness was found in probands (p=0.031). Significant correlations between the results of some neuropsychological tests and genes for neuro-/immunomodulators (IL-6, TNF-alpha) and the gene for the brain-derived neurotrophic factor (BDNF) were found. CONCLUSION: The study showed a statistically significant prevalence of A1 allele of the DRD gene in the hyperkinetic group. We also found a significantly higher incidence of atypical DAT genotypes in the hyperkinetic group. Furthermore we found significant connections with particular gene polymorphisms which may hypothetically represent a neurodevelopmental risk factor in the etiopathogenesis of the disorder (IL-2, IL-6, TNF-alpha, BDNF). We further found a connection of the M235 polymorphism of the AGT (angiotensinogene) gene to positive family history of psychiatric illness (p=0.031). As for cognitive characteristics, we identified three subtypes with different cognitive performance profiles. This finding shows interindividual variability of cognitive style in the group of hyperkinetic boys.

Department of Psychiatry Faculty Hospital and Masaryk University Brno Czech Republic