A specific pattern of methylations (with CpG 2 following either CpGs 1 + 3 or CpG 6 at the DAT1 5′-UTR) has been associated, therefore, with the likelihood of an internalizing or externalizing developmental trajectory entailing ADHD-like psycho-pathological characteristics. This evidence concerns the gene SLC6A3 and attention deficit-hyperactivity disorder.