The meta-analyses resulted in methylome-wide significant (FDR<0.05) ADHD associations in CD8T cells (RPL31P11 and KCNJ5) for peripheral blood, and, in cord blood, in monocytes (PDE6B), CD8T cells (KCNA3 and HAND2), and NK cells (KIFC1). Here, KCNA3 is linked to attention deficit-hyperactivity disorder.