The potassium (Kv) channel‐interacting protein 4 (KCNIP4) (4p15.2) has been implicated in attention‐deficit/hyperactivity disorder (ADHD),77 while PCDH9 (Protocadherin 9) (13q21.32) is a transmembrane protein that mediates cell adhesion in neural tissues and neuronal synaptic junction signaling.78 This evidence concerns the gene PCDH9 and attention deficit-hyperactivity disorder.