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). This evidence concerns the gene ARRB1 and depressive symptom measurement.