Lower ARRB1 mRNA and β-arrestin 1 protein levels have been observed in murine models of depression, as well as in human mononuclear leukocytes of depressed patients, compared to healthy controls (Avissar et al., 2004; Matuzany-Ruban et al., 2005; Golan et al., 2013; Lipina et al., 2013; Mendez-David et al., 2013). The gene discussed is ARRB1; the disease is major depressive disorder.