SYNE1 and attention deficit-hyperactivity disorder: SNPs that appeared only in patients with only ADHD (Group 2) are chr1:200968575, located on the KIF21B gene; chr2:206480353, located on the PARD3B gene; chr6:152665271, located on the SYNE1 gene; and chr16:23634293, located on the PALB2 gene, with a low variant frequency (0.12) compared to that of other SNPs detected in this study.