Though the DAT1 3'UTR is lengthier than the transcript's entire coding region, is a likely target for modulating DAT1 translation, and has been associated with symptoms of ADHD, there exists the possibility of linkage disequilibrium between the DAT1 3'UTR and a separate, yet unidentified, causal genetic element. This evidence concerns the gene SLC6A3 and attention deficit-hyperactivity disorder.