This imbalance plays a crucial role in an individual’s disease susceptibility, and studies on clinical samples have shown that DAT1 was associated with different psychopathological difficulties, from infancy to adulthood, including attention-deficit hyperactivity disorder (ADHD) [50,51,52,53], conduct disorder [54], affective disorders [55,56], post-traumatic stress disorder [57], and eating disorders [58,59]. This evidence concerns the gene SLC6A3 and attention deficit-hyperactivity disorder.