They found increased peripheral blood levels of catalase (CAT) and malondialdehyde (MDA), and reduced superoxide dismutase (SOD) activity in patients compared to controls, but no consistent differences were observed between treatment-responsive and treatment-resistant groups, suggesting that oxidative imbalance reflects a general pathophysiological feature of schizophrenia rather than a marker of treatment resistance [241]. Here, CAT is linked to schizophrenia.