SOD1 and major depressive disorder: In fact, in MDD, while most of the authors have generally described decreased levels of GPX and increased levels of malondialdehyde (MDA), as a lipid peroxidation marker [123, 126], there are also controversies regarding the specific activity of some antioxidant enzymes such as SOD, which was reported to be decreased in patients with MDD [56], showing no significant modifications when compared to controls [127] or a significant increase in most of the studies [123, 124, 128, 129].