More than half of schizophrenia patients have a vitamin D deficiency, according to a recent systematic review.
A meta-analysis of 13 of the total 19 studies in the review revealed that schizophrenia patients had an average 5.91 ng/mL lower serum 25-hydroxyvitamin D (25[OH])D) levels than control participants, Ghazaleh Valipour of Isfahan (Iran) University, and her colleagues reported online (J. Clin. Endocrinol. Metab. 2014 [doi:10.1210/jc.2014-1887]).
The 19 studies, published between 1988 and 2013, measured serum vitamin D levels in schizophrenic patients, including those with schizoaffective or other schizophrenia spectrum disorders. The articles included 8 cross-sectional studies, 10 case-control studies, and 1 nested case-control study, with a total of 2,804 participants aged 18-65. Sample sizes ranged from 17 to 848 participants.
A second meta-analysis of 8 of the 19 studies found that 65% of schizophrenia patients had a vitamin D deficiency, with prevalence ranging from 14% to 98% across studies. A third meta-analysis of eight studies found participants with a vitamin D deficiency had twice the odds of schizophrenia (odds ratio, 2.16) than those with sufficient levels of vitamin D, with studies’ odds ratios ranging from 0.6 to 13.6. Differences in findings across the studies could not be attributed to study design, the patient’s hospitalization status, study quality or study location; but use of 25-dihydroxyvitamin D3 (25[OH]D3) to measure serum levels explained some variation.
However, in all but one study, odds ratios "were calculated using the prevalence of schizophrenia in vitamin D–sufficient and –deficient persons," the researchers wrote. "Therefore, causality cannot be inferred from this finding because in most studies the exposure and the outcome coexisted."
The research was funded by the Research Council of the Food Security Research Center at Isfahan University. The authors had no disclosures.