SLC6A3 and attention deficit-hyperactivity disorder: As a result of both the studies here compared [8,10], we can conclude that the DAT1 gene may play an important role in identifying markers in ADHD: It can be used as a predictor of more or less severity of the disorder (in terms of rigidity vs. flexibility of behavioral symptoms), depending on the particular dynamic methylations it undergoes at its 5′-UTR.