title: Serum vitamin D levels in relation to schizophrenia: a systematic review and meta-analysis of observational studies.
abstract: BACKGROUND
  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.
  
  
  OBJECTIVE
  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.
  
  
  METHODS
  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).
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  We found a strong association between vitamin D deficiency and schizophrenia. However, randomized clinical trials are required to confirm our findings.
authors: Food Security Research Center and Department of Community Nutrition, School of Nutrition and Food Science, Isfahan University of Medical Sciences, Isfahan, Iran 81745.
authors: Ghazaleh
authors: G
authors: Valipour
authors: Parvane
authors: P
authors: Saneei
authors: Ahmad
authors: A
authors: Esmaillzadeh
mesh_terms: D006801:Humans; D064887:Observational Studies as Topic; D015995:Prevalence; D012559:Schizophrenia / Q000453:epidemiology* / Q000378:metabolism*; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000453:epidemiology* / Q000378:metabolism*
chemical_list: D014807:Vitamin D