SLC29A4 and attention deficit-hyperactivity disorder: Together with the low-affinity, high-capacity transporters OCT and PMAT, they play a major role in regulating monoamine (MA) signaling4,5, making them principal targets for medications against several psychiatric disorders such as Attention-Deficit/Hyperactivity Disorder (ADHD), anxiety and major depression6,7 as well as targets for psychoactive recreational drugs.