Given the biological relevance of dopamine in ADHD pathophysiology, numerous studies have explored these dopamine-related genetic pathways further, including DRD4, DRD5, DAT1,5-HTT/SLC6A4, HTR1B, NET1, SNAP-25, and BDNF (26, 27). This evidence concerns the gene SLC6A4 and attention deficit-hyperactivity disorder.