Attention-deficit hyperactivity disorder (ADHD)-like clinical characteristics can exist in individuals with ASD and epileptic encephalopathy who have alterations in CHD2 [41], GRIN2A [26], PCDH19 [36, 42], SLC6A1 [29], and STXBP1 [43]. This evidence concerns the gene STXBP1 and attention deficit-hyperactivity disorder.