Objectives: The presence of certain alleles in polymorphisms of the dopamine receptor gene (DRD4) and the dopamine transporter gene (DAT1) increases a child's risk of developing ADHD or another mental disorder. We investigated whether or not the severity of the above-mentioned dopaminergic polymorphisms is associated with regulatory disorders in infancy.
Methods: The Mannheim Study of Children at Risk interviewed parents of three-month-old children in depth about behavior problems and observed parents and children in various situations as well. The genotyping for DRD4 and DAT1 polymorphisms was carried out in the children by means of standard methods at the age of 15 years. Investigated were 300 children (145 boys, 155 girls) for whom complete datasets existed with regard to the research question.
Results: Isolated regulatory problems were observed in 54 boys, respectively in 64 girls (37.2%, respectively 41.3%), while 17 boys, respectively 19 girls (11.7%, respectively 12.3%) exhibited multiple regulatory problems. In boys, the presence of the DRD4-7r allele was significantly associated with the occurrence of multiple regulatory problems (p = .04). No such association was found with regard to isolated regulatory problems, or among girls. There was no association for either gender between the DAT1 genotype (10r/10r vs. rest) and isolated or multiple regulatory problems.
Conclusions: The result must be replicated in an independent sample before any conclusions can be drawn.