Lack of sunshine vitamin linked to schizophrenia risk

BMJ Group News

Rates of the mental illnessschizophrenia might be substantially reduced if all pregnant women took vitamin D supplements, researchers say. The claims come in a research paper linking low vitamin D levels at birth with a two-fold increase in the chances of getting schizophrenia in later life.

What do we know already?

Schizophrenia is a serious mental illness that causes hallucinations and delusions. Scientists have been unable to find a single cause for schizophrenia, but it’s likely to be a combination of genes and environmental triggers.

Schizophrenia is more common among people born in the winter or spring. It’s also more common among people whose parents moved to the UK from hotter countries such as Africa or the Caribbean, and in people who grew up in the city compared with the countryside.

All these factors have led scientists to speculate that the linking factor may be the ‘sunshine vitamin’, vitamin D. Vitamin D is made by the body when sunlight hits the skin. Vitamin D is important for making strong bones, but it may also be important for brain development.

The theory is that pregnant women who get less sun - for example women who are pregnant over the winter - will make less vitamin D. Their babies may be deficient in vitamin D, and this may make them vulnerable to schizophrenia in later life.

However, until now there’s been no research directly comparing vitamin D levels at birth with later diagnosis of schizophrenia. New research from Denmark used the vitamin D levels in stored blood samples from newborn babies born since 1981. Researchers compared samples from people with schizophrenia with people born on the same day who don’t have schizophrenia.

What does the new study say?

People who’d had the lowest levels of vitamin D at birth were twice as likely to get schizophrenia, compared with those with higher levels. The researchers say the findings can’t be explained by factors such as family history of mental illness, being born prematurely, or low birth weight.

However, the findings are complicated, because people with the highest vitamin D levels at birth were also at increased risk of schizophrenia. This finding was unexpected, and makes it harder to be sure that the theory about vitamin D being a cause of schizophrenia is right.

If it is right, the researchers estimate that 44 percent of the cases of schizophrenia in their study could have been avoided if people had had the optimum levels of vitamin D. They say that the idea that such a serious illness could be substantially reduced by simple nutritional supplements is “tantalising”. If vitamin D supplements did work, the benefits would be even bigger among groups of people with higher rates of schizophrenia. For example, supplements could theoretically lead to an 87 percent reduction in schizophrenia rates among African Caribbean people living in the UK.