Oxidative stress markers in bipolar disorder: A meta-analysis

Backgaround: Oxidative stress is thought to mediate neuropathological processes of a number of neuropsychiatric disorders and recent data suggest that oxidative stress may be involved in the pathophysiology of bipolar disorder (BD). In the present investigation, we conducted a meta-analysis of studies that evaluated markers of oxidative stress in individuals with BD, as compared to healthy controls. Methods: A Medline search was conducted to identify Studies that measured peripheral markers of oxidative stress in bipolar disorder. Data were subjected to meta-analysis using a random effects model to examine the effect sizes of the pooled results. Bias assessment (Egger's test) and assessment of heterogeneity (l(2)) were also carried out. Results: Thiobarbituric acidic reactive substances (TBARS) (p = 0.001) as well as NO activity 0.02) were significantly increased in BD with a large effect size for TBARS and a moderate effect size for increase in NO. No significant effect sizes were observed for the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase (all p>0.05). Limitations: Some caution is warranted in interpreting these results: (1) Egger's test was positive for SOD, suggesting that SOD results may have been influenced by a publication bias. (2) We analyzed the absolute values of each antioxidant enzyme separately and the literature suggests that an imbalance between the antioxidant enzymes is a better indication of the presence of oxidative stress. Conclusions: The present meta-analysis Suggests that oxidative stress markers are increased in BD and that oxidative stress may play a role in the pathophysiology of BD. (C) 2008 Elsevier B.V All rights reserved.