Objective Bipolar disorder (BD) is a chronic mood disorder characterized by recurrent episodes that has a lifetime prevalence of 0.4– 5.5%. The neurochemical mechanism of BD is not fully understood. Oxidative stress in neurons causes lipid peroxidation in proteins associated with neuronal membranes and intracellular enzymes and it may lead to dysfunction in neurotransmitter reuptake and enzyme activities. These pathological processes are thought to occur in brain regions associated with affective functions and emotions in BD. The relationship between the number of manic episodes and total oxidant-antioxidant capacity was investigated in this study. Methods Eighty-two BD patients hospitalized due to manic symptoms and with no episodes of depression were enrolled in the study. Thirty of the 82 patients had had their first episode of mania, and the other 52 patients had had two or more manic episodes. The control group included 45 socio-demographically matched healthy individuals. Serum total antioxidant capacity (TAC) and total oxidant capacity (TOC) measurements of the participants were performed. The oxidative stress index (OSI) was calculated by TOC/TAC. Results There were no significant differences in OSI scores between BD patients with first-episode mania and BD patients with more than one manic episode. However, OSI scores in both groups were significantly higher than in the control group. TOC levels of BD patients with first-episode mania were found to be significantly higher than TOC levels of BD patients with more than one manic episode and healthy controls. There were no significant differences in TAC levels between BD patients with first-episode mania and BD patients with more than one manic episode. TAC levels in both groups were significantly higher than in the control group. Conclusion Significant changes in oxidative stress indicators were observed in this study, confirming previous studies. Increased levels of oxidants were shown with increased disease severity rather than with the number of manic episodes. Systematic studies, including of each period of the disorder, are needed for using the findings indicating deterioration of oxidative parameters.
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