On this basis, it has been proposed that stress exposure could increase susceptibility to depression via generation of inflammatory PGs generated by COX-2; a contention in line with the neuroimmune hypothesis of depression (Felger and Miller, 2014; Haroon et al., 2012; Miller et al., 2009; Raison and Miller, 2013) and the aforementioned clinical efficacy of COX-2 inhibition in MDD. This evidence concerns the gene PTGS2 and major depressive disorder.