Association of dopamine D4 receptor (DRD4) gene with attention-deficit/hyperactivity disorder (ADHD) in a high-risk community sample:: a longitudinal study from birth to 11 years of age

Background: In recent years, a growing number of studies has focused on the dopamine D4 receptor gene (DRD4) as mediating the susceptibility to attention-deficit/hyperactivity disorder (ADHD). While their results are contradictory, the reason for this inconsistency remains as yet unclear. Method: The present study sought to examine the association between ADHD and the DRD4 exon III polymorphism during child development using longitudinal data from a high-risk community sample (n=265, 129 females, 126 males) who have been followed from birth to 11 years of age. Results: Higher rates of ADHD were observed in boys with the 7 repeat allele of exon III than in boys with other alleles at the ages of 4 1/2 (Fisher's exact test, p=.061), 8 (p=.026), and 11 years (p=.005). Boys with this allele also exhibited higher rates of persistent disorder (p=.024). In girls, a trend towards an association (p=.055) with the 7 repeat allele emerged only at preschool age. Conclusions: These findings provide additional evidence for the role of the dopamine D4 receptor in ADHD during the course of child development.