Oxidative stress parameters and antioxidants in patients with bipolar disorder: Results from a meta‐analysis comparing patients, including stratification by polarity and euthymic status, with healthy controls

Objective To investigate oxidative stress markers and antioxidants in bipolar disorder (BD). Methods Electronic MEDLINE/PubMed/Cochrane‐Library/Scopus/TripDatabase search until 06/30/2019 for studies comparing antioxidant or oxidative stress markers between BD and healthy controls (HCs). Standardized mean differences (SMD) and 95% confidence intervals (CIs) were calculated for ≥3 studies. Results Forty‐four studies (n = 3,767: BD = 1,979; HCs = 1,788) reported on oxidative stress markers malondialdehyde (MDA), thiobarbituric acid reactive substances (TBARS), and total nitrites; antioxidants glutathione (GSH), uric acid, and zinc; or antioxidantenhancing enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), and GSH‐transferase (GST). Compared with HCs, BD was associated with higher GST (P = .01), CAT (P = .02), nitrites (P