Building on the habenular neural circuit physiology established by pioneering studies (Hikosaka, 2010; Kobayashi et al., 2013; Lee and Goto, 2013), the selective expression of Elfn1 corroborates that clarification of the role of Elfn1 in habenular neural circuits would contribute to a better understanding of ADHD pathophysiology. The gene discussed is ELFN1; the disease is attention deficit-hyperactivity disorder.