Undergraduate students are frequently afflicted by major depressive disorder (MDD). Oxidative and nitrosative stress (O&NS) has been implicated in the pathophysiology of MDD. There is no information regarding whether mild outpatient MDD (SDMD) and first episode SDMD (FE-SDMD) are accompanied by O&NS. The current study compared lipid hydroperoxides (LOOH), malondialdehyde (MDA), advanced protein oxidation products, nitric oxide metabolites (NOx), thiol groups, plasma total antioxidant potential (TRAP), and paraoxonase 1 activities among SDMD and FE-SDMD patients versus healthy controls. We found that SDMD and FE-SDMD exhibit elevated MDA and NOx, and decreased TRAP and LOOH as compared with controls. There was a significant and positive correlation between O&NS biomarkers and adverse childhood experiences (ACEs), and negative life events (NLEs). O&NS pathways, NLEs and ACEs accounted for 51.7% of the variance in the phenome of depression, and O&NS and NLS explained 42.9% of the variance in brooding. Overall, these results indicate that SDMD and FE-SDMD are characterized by reduced total antioxidant defenses and increased aldehyde and NOx production. The combined effects of oxidative and psychological stressors are substantially associated with the manifestation of SDMD.