Deficiency of vitamin D doubles the risk of schizophrenia, a new research shows.

Researchers examined 19 observational studies that involved 2,804 adult participants. The team assessed the association between vitamin D and schizophrenia. They found that those diagnosed with schizophrenia had significantly lower levels of vitamin D in the blood.

The study analysis showed that the average difference in vitamin D levels between schizophrenic patients and those with adequate vitamin D in their bloodstreams was -5.91 ng/ml. Researchers said that people who lacked vitamin D were 2.16 times more likely to be schizophrenic than those with sufficient levels.

Moreover, the researchers found that 65 percent of participants who had schizophrenia also had vitamin D deficiency.

"This is the first comprehensive meta-analysis to study the relationship between the two conditions," researcher Ahmad Esmaillzadeh, PhD, at the Isfahan University of Medical Sciences in Isfahan, Iran, said in a press release. "When we examined the findings of several observational studies on vitamin D and schizophrenia, we found people with schizophrenia have lower vitamin D levels than healthy people. Vitamin D deficiency is quite common among people with schizophrenia."

"There is a growing trend in the nutrition science field to consider vitamin D and its relationship to conditions such as diabetes, cancer, heart disease and depression," Esmaillzadeh said. "Our findings support the theory that vitamin D may have a significant impact on psychiatric health. More research is needed to determine how the growing problem of vitamin D deficiency may be affecting our overall health."

The latest findings are published in the Journal of Clinical Endocrinology & Metabolism.