SLC6A3 and attention deficit-hyperactivity disorder: Developmental aspects may also change gene expression, as, in children, the 6R–10R-allele has been described to be a risk factor for ADHD, while in adults the 6R–9R allele was associated with ADHD [31], [32], pointing towards a differential decay of dopamine transporter expression with development [28], i.e. a steeper age-related decrease of dopamine binding capacity for non 6R–10R carriers.