ARRB1 and major depressive disorder: Given that ARRB1 mRNA and β-arrestin 1 protein levels have been previously associated with depression and ATD treatment (Avissar et al., 2004; Matuzany-Ruban et al., 2005; Golan et al., 2013), variants annotated as likely to lie in a functional element—and thus be more likely to impact ARRB1 expression or β-arrestin function—were prioritized using RegulomeDB (Boyle et al., 2012).