Researchers found that study participants with vitamin D deficiency were more likely to develop schizophrenia than those with normal vitamin D levels.
Exactly what causes the condition is unclear, although previous studies have suggested that imbalances of chemical reactions in the brain, genetics and environmental factors may play a part.
The researchers of this latest study, including Ahmad Esmaillzadeh, PhD, of the Isfahan University of Medical Sciences in Isfahan in Iran, set out to investigate whether there is an association between vitamin D deficiency and schizophrenia.
Vitamin D is a fat-soluble vitamin found in certain foods, such as oily fish. However, the body's main source of vitamin D is from the sun.
According to the team, schizophrenia tends to be more prevalent in cold climates with high latitudes. Since vitamin D levels are primarily influenced by sunlight exposure, this spurred their research.
Subjects with vitamin D deficiency '2.16 times more likely to have schizophrenia'
To reach their findings, recently published in the Journal of Clinical Endocrinology & Metabolism (JCEM), Esmaillzadeh and colleagues analyzed 19 observational studies that looked at the association between vitamin D and mental health conditions, including schizophrenia.
All study participants - including 2,804 adults with or without mental health conditions - underwent blood tests that disclosed vitamin D levels in their blood.
Esmaillzadeh says the study is "the first comprehensive meta-analysis" to study the relationship between vitamin D deficiency and schizophrenia.
The researchers found that, compared with healthy participants, individuals with schizophrenia had much lower levels of vitamin D in their blood.
Around 65% of patients with schizophrenia had vitamin D deficiency, according to the researchers. In detail, they found that vitamin D levels in subjects with schizophrenia were 5.91 ng/ml lower than those of healthy participants. The researchers calculated that participants with vitamin D deficiency were 2.16 times more likely to have schizophrenia, compared with those whose vitamin D levels were normal.
Commenting on the team's findings, Esmaillzadeh says:
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."
However, Esmaillzadeh told Medical News Today that it is possible schizophrenia could cause vitamin D deficiency rather than have the opposite effect.
"Due to the observational nature of studies included in our meta-analyses, we can not strongly declare that vitamin D deficiency causes schizophrenia," he said.
"However, findings of two important epidemiologic study by McGrath et al., (neonatal vitamin D status and risk of schizophrenia, and vitamin D supplementation during the first year of life and risk of schizophrenia) confirms that lower levels of vitamin D in early stages of life is a risk factor of developing schizophrenia later in life. Also, several animal studies have shown that vitamin D deficiency can cause brain impairments that might lead to schizophrenia. Therefore, more prospective studies and controlled clinical trials are needed in this regard."
Esmaillzadeh told us that the next steps from this research may be to investigate the role of vitamin D supplementation among schizophrenia patients, or look at the link between maternal and neonatal vitamin D levels and the risk of schizophrenia later in life.
Medical News Today recently reported on a mouse study published in the journal Cell Stem Cell, which detailed how certain genetic variations may increase the risk of schizophrenia. Another recent study found that a gene called SETD1A may play an important role in the development of schizophrenia.