Oxidative and nitrosative stress markers in obsessive–compulsive disorder: a systematic review and meta-analysis

Objective: Obsessive–compulsive disorder (OCD) is a chronic, prevalent, and highly impairing psychiatric illness. Although the pathophysiology of OCD remains unknown, pathways involved in oxidative and nitrosative stress (O&NS) have been implicated. The present study aims to systematically review the literature for quantitative evidence that patients with OCD have altered measures of blood O&NS markers. Methods: Independent random-effects meta-analyses using standardized mean differences were conducted to assess each marker separately. Additionally, data from multiple markers were pooled together in a meta-analysis for measures of oxidant activity and another for measures of antioxidant activity. Results: Thirteen studies met inclusion criteria, involving 433 OCD patients and 459 controls. Eleven blood O&NS markers were eligible for independent quantitative analyses. We found that, in OCD patients, the oxidant markers 8-hydroxydeoxyguanosine and malondialdehyde, and the antioxidants glutathione peroxidase and superoxide dismutase, were significantly increased while total antioxidant status, vitamin C, and vitamin E were significantly decreased, when comparing with controls. Regarding pooled meta-analyses, we found a statistically significant increase in oxidant markers, but non-significant results regarding antioxidant markers. Conclusions: Our meta-analysis suggests that OCD patients have a systemic oxidative imbalance that is not adequately buffered by the antioxidant system. Additional studies are needed in order to support this association.