PTGS2 and major depressive disorder: Accordingly, adjunctive treatment with the COX-2 inhibitor, celecoxib (CBX), has been reported to lead to improved overall outcome in major depressive disorder (MDD) (Akhondzadeh et al., 2009; Abbasi et al., 2012; Hosseini et al., 2014; Müller et al., 2006; Fond et al., 2014; Müller, 2019).