Among the 112 ADHD subjects, the genotype frequencies (A/A homozygous, A/T heterozygous, and T/T homozygous) of the SLC6A2 -3081(A/T) polymorphism were 25.9%, 53.6%, and 20.5%, respectively (Table 2). This evidence concerns the gene SLC6A2 and attention deficit-hyperactivity disorder.