ANKK1 and attention deficit-hyperactivity disorder: Association studies described a connection between ADHD symptomatology with the presence of the ANKK1 TaqI A1 allele [47], which confirmed previous observations made in 1991 by Comming et al. in patients with ADHD and their relatives, where the frequency of the TaqI A1 allele occurrence in the researched group was 49%, whereas in the control group it was 27%.