IFNB1 and attention deficit-hyperactivity disorder: SLC9A9, whose encoded protein localizes to the late recycling endosomes and plays an important role in maintaining cation homeostasis (RefSeq, Mar 2012), is associated with multiple pharmacogenomic traits related to neurological diseases, including response to cholinesterase inhibitor in AD [37], response to interferon beta in MS [38], response to angiotensin II receptor blockade therapy [39], and multiple complex diseases including attention-deficit/hyperactivity disorder [40], autism [41], and non-alcoholic fatty liver [42].