Vitamin D deficiency and Schizophrenia in Adults: A Systematic Review and Meta-analysis of Observational Studies

Schizophrenia is a heterogeneous disorder in which there is an interaction between genetic and environmental factors. Accumulating data show that there may be an association between vitamin D deficiency and schizophrenia. We conducted an updated meta-analysis to investigate the relationship between schizophrenia and blood vitamin D level. All published observational articles have been searched from five databases until September 2019. In total, 36 articles with a total of 12528 participants were included in this study. Patients with schizophrenia have significantly lower levels of vitamin D than controls. The subgroup analyses based on study design, hospitalization status, quality score, type of biomarker [25-hydroxyvitamin D or 25-hydroxyvitamin D-3], and the country did not explain between-study heterogeneity; however, meta-regression on match factors indicted that match of BMI could account for some degree of heterogeneity. No significant differences in publication bias were observed. Also, subjects with schizophrenia were more likely to have vitamin D deficiency or insufficiency compared to controls. In conclusion, our analyses are consistent with the hypothesis that vitamin D deficiency is associated with schizophrenia. More well-designed randomized control trials are needed to determine whether this association is causal.