In particular, the metabotropic glutamate receptor 7 (GRM7), which is widely expressed in brain regions relevant to ADHD such as the cerebral cortex, the hippocampus and the cerebellum51,70 and has been associated with the disorder71–73, was also found among the top hits in a prior GWAS of MPH efficacy13, thus supporting the role of the glutaminergic system as a moderator of treatment outcome. This evidence concerns the gene GRM7 and attention deficit-hyperactivity disorder.