In some other studies, no association between the rs6675281 polymorphism and ADHD was observed.18-21 Finally in one investigation on the effects of DISC1 variants, it was implicated that the rs6675281 polymorphism’s alleles affect the expression level of DISC1, so that the T allele carriers had significantly higher levels of DISC1 expression in comparison with C allele carriers.22,23. Here, DISC1 is linked to attention deficit-hyperactivity disorder.