People who suffer from Vitamin D deficiency are twice as likely to be diagnosed with schizophrenia as those who have sufficient levels of the vitamin, according to new research.
Scientists who examined 19 studies involving more than 2,000 adults found 65% of participants who had the mental health condition were also Vitamin D deficient. Those with schizophrenia had "significantly" lower levels of Vitamin D in their blood compared to those who did not.
People with Vitamin D deficiency were more than twice as likely to have schizophrenia than those with sufficient levels in their blood, according to the study published in the Endocrine Society's Journal of Clinical Endocrinology & Metabolism.
The skin naturally produces Vitamin D after exposure to sunlight and more than a billion people worldwide are thought to have deficient levels of vitamin D due to limited sunshine exposure.
Schizophrenia, with symptoms that can include delusions and hallucinations, is more common in high latitudes and cold climates and researchers had been working on the theory that Vitamin D deficiency could be connected to the long term mental health condition.
"This is the first comprehensive meta-analysis to study the relationship between the two conditions," Dr Ahmad Esmaillzadeh, of the Isfahan University of Medical Sciences in Isfahan, Iran and one of the research authors, said.
"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."
He added: "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.
"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 findings come after the National Institute for Health and Care Excellence (Nice) revealed earlier this year that millions of Britons are not getting enough vitamin D - putting them at greater risk of developing rickets and bone deformities.
Low levels of vitamin D may indicate a higher risk of dying from heart disease cancer and other illnesses, according to a study published last month.