SLC6A9 and attention deficit-hyperactivity disorder: No correlation between 23 genes identified as targets of methylphenidate and ADHD GWAS gene-level summary statistics. Within the loci associated with ADHD 5 druggable genes encode proteins interacting with FDA-approved or clinical trial drugs:PTPRF, TIE1, MPL, SLC6A9 and KCNH3: Hegvik et al., 2019.