SOD1 and major depressive disorder: In adolescents diagnosed with MDD, those who had attempted suicide exhibited elevated serum superoxide dismutase (SOD) activity, reduced nitric oxide (NO) levels, more severe anxiety and depressive symptoms, worse sleep quality, increased exposure to adverse life events, less effective coping strategies, worse parental attachment, more severe alexithymia, and more impulsivity when compared to their counterparts without a history of SA (all p<0.05).