MAOA and attention deficit-hyperactivity disorder: Interestingly, the positive association with ADHD was also confirmed when the predisposing genotypes of the two MAOA gene polymorphisms (GG of rs6323 and TT of rs1137030) were considered together (23.7% (19/80) vs. 10% (8/80) p = 0.0238, OR = 2.80, CI: 1.15 to 6.85).