A considerable proportion of patients with these types of epilepsies also have ID and/or behavioral problems (ADHD, ASD, anxiety, depression) (Borgatti et al., 2004; Steinlein et al., 2007; Akanuma et al., 2008; Tovia et al., 2011) which supports a common genetic etiology and accordingly suggest KCNQ3 (and KCNQ2) as candidate susceptibility genes for ID and various psychiatric disorders. Here, KCNQ2 is linked to attention deficit-hyperactivity disorder.