Vitamin D Deficiency as a Risk Factor for Schizophrenia: A meta-analysis of Observational Studies

Abstract Background: Schizophrenia is a heterogeneous disorder in which there is interaction between genetic and environmental factors. Study have found that vitamin D deficiency is a risk factor for schizophrenia. We conducted a meta-analysis to investigate the relationship between schizophrenia and blood vitamin D level. Methods: A systematic review and meta-analysis have been conducted. All published observational articles have been searched from PubMed, Web of Science, Scopus, Cochrane library and Embase until September 2019. The Newcastle-Ottawa scale was used to examine the quality of the included studies. Results: A total of 38 articles have been included in this study. The lower level of vitamin D was found in people with schizophrenia compared with controls (WMD =-4.50, 95%CI [-6.69, -2.32]). Subgroup analyses based on study design, the patient’s hospitalization status, quality of the study, outcomes, and the country explained part of between-study heterogeneity. No significant differences in publication bias were observed. The overall prevalence of vitamin D deficiency and insufficiency in schizophrenic patients were 66%, 95%CI [57%–76%] and 76%, 95%CI [69%, 83%], respectively. Subjects with schizophrenia were more likely to have vitamin D deficiency or vitamin D insufficiency compared to controls (2.03, 95%CI [1.49, 2.77]; 2.43, 95%CI [1.40, 4.23]). Conclusion: The results of this systematic review show that low vitamin D levels might contribute to the development of schizophrenia. The prevalence of vitamin D deficient or insufficient in schizophrenia was higher than that in healthy controls or another psychotic disease .