CYP2D6 and attention deficit-hyperactivity disorder: Further in the subgroup analysis, ADHD RS-IV-J:I in the low metabolizer group (CYP2D6 IMs) in placebo group, − 6.1 ± 11.1 (n = 9) vs. the dose of TS-141120 mg was − 11.2 ± 9.5 (n = 11).