H2BC15 and attention deficit-hyperactivity disorder: Among 146 genes, there were seven genes common to four disorders, including GLT8D1, KCNB1, GABBR1, HIST1H1B, HIST1H2BN, and HIST1H4L in SCZ, DEP, BD, and ASD, and DCC in ADHD, ASD, DEP, and SCZ.