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J Clin Endocrinol Metab. 2014 Oct;99(10):3863-72. doi: 10.1210/jc.2014-1887. Epub 2014 Jul 22.

Serum vitamin D levels in relation to schizophrenia: a systematic review and meta-analysis of observational studies.

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Food Security Research Center and Department of Community Nutrition, School of Nutrition and Food Science, Isfahan University of Medical Sciences, Isfahan, Iran 81745.



Although several observational studies have investigated the association between vitamin D status and schizophrenia, we are aware of no comprehensive meta-analysis in this regard.


We aimed to conduct a systematic review and a meta-analysis of observational studies to summarize the available data on the association between serum vitamin D levels and schizophrenia.


A systematic research on all published articles until October 2013 was conducted in PubMed, ISI (Web of science), SCOPUS, and Google Scholar. All observational studies that had measured serum vitamin D levels in schizophrenic patients were included in the systematic review. After considering exclusion criteria, we had 19 studies for the systematic review that were included in three separate meta-analyses: 1) a meta-analysis on mean levels of 25-hydroxyvitamin D [25(OH)D] (n = 13); 2) a meta-analysis on the prevalence of vitamin D deficiency (n = 8); 3) a meta-analysis on odds ratios (n = 8).


Findings from a meta-analysis on means revealed that the overall mean difference in serum 25(OH)D levels between schizophrenic patients and control participants was -5.91 ng/mL [95% confidence interval (CI) -10.68, -1.14]. Subgroup analyses based on study design, the patient's hospitalization status, study quality, and study location did not explain between-study heterogeneity; however, type of biomarker assessed [25-hydroxyvitamin D3 vs 25-hydroxyvitamin D (D2 & D3)] could account for some degree of heterogeneity. RESULTS from the meta-analysis on the prevalence of vitamin D deficiency indicated that the overall prevalence of vitamin D deficiency in schizophrenic patients was 65.3% (95% CI 46.4%-84.2%). Findings from the meta-analysis on odds ratios indicated that vitamin D-deficient persons were 2.16 times (95% CI 1.32, 3.56) more likely to have schizophrenia than those with vitamin D sufficiency. No evidence of heterogeneity was detected.


We found a strong association between vitamin D deficiency and schizophrenia. However, randomized clinical trials are required to confirm our findings.

[Indexed for MEDLINE]

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