Importantly, 8 of the 19 proteins that exhibit differential direction of expression in Flx-responders versus Flx-non-responders have been associated with MDD or antidepressant response (RPN-2, HSPA9, NPTN, AP1B1, UQCRC2, RACK1, TOLLIP, and TLN2 (McHugh et al., 2008; Suzuki et al., 2010; Voloboueva and Giffard, 2011; Andrus et al., 2012; Porter et al., 2012; Beesley et al., 2014; Seguini et al., 2014; Waiskopf et al., 2014; O’Donovan et al., 2015; Xu et al., 2016; Bhattacharya et al., 2017; Hung et al., 2017). This evidence concerns the gene AP1B1 and major depressive disorder.