People with schizophrenia are more likely to have been born in the winter or spring, compared to the summer or autumn. Various theories have been suggested to explain this, for example whether unborn babies are affected by winter viruses.Another hard-to-explain fact is the unusually high rate of schizophrenia among the children of people who migrate from hot countries to colder countries—notably from the Caribbean to the United Kingdom. Doctors wonder why these second-generation immigrants are more likely to suffer from schizophrenia than their parents.
A third aspect is that people who have an urban upbringing have a higher chance of schizophrenia than those who grow up in the countryside. Scientists theorize about the alienating effect of the urban lifestyle on mental health.But one theory might explain all these curious facts. Vitamin D (known as the sunshine vitamin because it’s made by chemical reactions in the skin when exposed to sunlight) is important for growing healthy bones. But, researchers suggest, it might also be important in developing healthy brain structures.
Could it be that babies whose mothers got less sunlight—because they were pregnant during the winter, or their dark skin was less able to synthesize vitamin D in colder northern latitudes, or their urban lifestyle meant they spent less time outdoors—were vitamin D deficient? And could this be the key to their increased risk of schizophrenia?Thanks to a new study we’re one step closer to finding out. Researchers from Denmark used the country’s health databases to study vitamin D levels in stored blood samples, taken from all newborn babies born in Denmark since 1981. They identified the blood samples from people who’d been diagnosed with schizophrenia in later life, then compared these with samples from people born on the same day, but who didn’t have schizophrenia.
The results showed a strong link. People with the lowest levels of vitamin D had twice the chance of developing schizophrenia as those with the optimum levels. The link could account for 43 percent of the cases of schizophrenia in the study, the researchers said. This is an exciting finding. Vitamin D supplements are cheap and readily available, although may be harmful if you take too much. If all pregnant women took extra vitamin D, could we reduce the numbers of people with schizophrenia by half?Sadly, we don’t know yet. There were some problems with the data—for example, the people with the highest levels of vitamin D also had a higher risk of schizophrenia, which was unexpected and throws doubt on the overall findings. Also, showing a link between low levels of vitamin D and schizophrenia doesn’t mean that one caused the other, or that vitamin D supplements would reverse the effect. But it’s a promising avenue for further research.
What you need to know. We can’t say from this study whether taking Vitamin D supplements during pregnancy will help cut the chances of your child getting schizophrenia. But some doctors recommend extra vitamin D during pregnancy or while you’re breast-feeding. Your needs for vitamin D supplements depend on where you live, and how much sun exposure you get. It’s best to talk to your health care provider before starting vitamin D supplements.—Anna Sayburn, patient editor, BMJ Group
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