PTGS2 and major depressive disorder: Several clinical trials and meta-analyses of trials have now confirmed the efficacy of COX-2 inhibition as an effective augmentation strategy to SSRIs in MDD (Abdallah et al., 2015; Akhondzadeh and Jafari, 2010; Akhondzadeh et al., 2009; Faridhosseini et al., 2014; Fond et al., 2014; Muller et al., 2006).