SLC6A3 and attention deficit-hyperactivity disorder: Our explorative 3-way interaction analysis in the cohorts combined (N = 2434) investigating the effect DAT1 9-6 haplotype, diagnostic status, and age suggests that carriership of the 9-6 haplotype predisposes to a slower age-related decay of striatal volume, which is specific for ADHD patients (Fig. 1).