Understanding links: Babies with low vitamin D may have high risk of mental disorders
Australian researchers say they’ve found convergent evidence babies born with vitamin D deficiency are at a higher risk of developing ADHD, schizophrenia, and autism.
The largest study of its kind has found convergent evidence babies born with a vitamin D deficiency have a higher risk of developing mental health disorders including ADHD and schizophrenia later in life.
The study was headed by psychiatrist Professor John McGrath who is with the Queensland Centre for Mental Health Research and the Queensland Brain Institute at the University of Queensland. His main areas of research are schizophrenia and the effect of vitamin D on the brain.
His team examined population data from Denmark, finding a significant inverse relationship between vitamin D and schizophrenia, ADHD and autism. Those findings support the hypothesis that adequate levels of neonatal vitamin D could reduce the incidence of a range of neurodevelopmental disorders.
“We found evidence that people with lower vitamin D concentration as a baby had an increased risk of schizophrenia, ASD (autism spectrum disorder) and ADHD,” Professor McGrath said.
Although he points out that this suggests an elevated risk, it does not explicitly mean all babies born with low vitamin D will go on to develop such disorders.
“Previous research had linked neonatal vitamin D deficiency with an increased risk of schizophrenia and autism, but this study examined a wider range of mental disorders, and included evidence based on two vitamin D-related biomarkers and related genetics.”
The study, funded by The Danish National Research Foundation, was a joint project between UQ, the National Centre for Register-Based Research at Aarhus University, and the State Serum Institute in Denmark. This time, researchers considered both classic vitamin D levels, the type people are commonly tested for, as well as concentrations of the vitamin D-binding protein.
This was the largest population study of its kind, with researchers examining the vitamin D status of 71,793 babies born between 1981 and 2005, and then followed them to see which ones developed mental health disorders during childhood or early adulthood. Professor McGrath says while there are many factors that can lead to a person developing the disorders, and this may be only one factor, the findings provide important insights.
“I’ve been looking for the causes of schizophrenia, and clearly there’s lots and lots; it’s not one clean, simple disorder with one cause as (there are) many, many causes, genetic and environmental,” Professor McGrath says.
“We’ve known for well over 50 years now that schizophrenia is a disorder of brain development, even though the symptoms don’t emerge until after puberty or often they emerge into the early 20s. We can see evidence that a subset of people with schizophrenia have had something go wrong in early life, even before they’re born.
“So, I thought, maybe vitamin D would be a candidate because one clue we’ve known since about 1920 that people with schizophrenia tend to be born in winter and spring, a little bit more than they should.”
His team then did what is called a “thought experiment”, or hypothetical reasoning. Based on the data they examined, they considered what percentage of those cases could be prevented if the baby was born with adequate levels of vitamin D.
“Our hypotheses suggests we could prevent 15 per cent of cases of schizophrenia and 9 per cent of ADHD and 5 per cent of autism.
“Many pregnant women are taking folate before they get pregnant, and many pregnant women are taking folate and iron when they are pregnant. And so I think putting a small dose of vitamin D will be good for the mother’s bones and also good for the baby’s bones and it may also be useful for healthy brain development.”
Tim Jones is the RACGP chair of Specific Interest Child and Young Person’s Health group. He was not involved in the study but has reviewed the research paper and says the findings build on existing understandings of vitamin D and development, much of which has been uncovered by Professor McGrath.
“This study is building on some of the emerging data we’ve been looking at for about five to 10 years now, where we have had some curiosity about what long-term role vitamin D may play, particularly for pregnant and breastfeeding women,” Dr Jones says.
“There are some associations developing here, things that we wonder if they may be linked, but we do not have definite proof that one is definitely causing the other.
“We’ve known for a long time that vitamin D does play an important role in development, particularly of bone development, potentially in nerve development too. And so we wouldn’t be surprised if there are some links here where it’s one of many factors playing a role. But it’s an easy-to-modify factor for people wishing to reduce the chance of this happening.”
Vitamin D is found in some foods, though it mostly forms when skin is exposed to UV from sunlight. However, Australia already has high UV levels and the warmer climate means people are less likely to be deficient in vitamin D than those living in cooler climes like Denmark.
Australians also need to be wary of sun damage from too much UV exposure.
“We are no longer looking at levels of sun exposure or skin colour as predictive of what your vitamin D is going to be like when you’re pregnant,” Dr Jones says.
“We would now universally just recommend vitamin D supplementation for women who are starting to try to fall pregnant and also during their pregnancy.”
In advice published by the Cancer Council, it suggests people in Australia can get adequate levels of vitamin D through regular incidental exposure to the sun.
“When the UV index is 3 or above (such as during summer), most people maintain adequate vitamin D levels just by spending a few minutes outdoors on most days of the week,” the Cancer Council says.
“In late autumn and winter in some southern parts of Australia, when the UV index falls below 3, spend time outdoors in the middle of the day with some skin uncovered. Being physically active (gardening or going for a brisk walk) also helps boost vitamin D levels.”
However, the group also recommends sun protection when the UV reaches three or above.
Professor McGrath has dedicated much of his working life to better understanding both of schizophrenia and the influence of vitamin D. This study is his largest and final piece of work before retiring and he hopes his body of work provides the next generation of scientists with even more pieces of the puzzle to better understand, and therefore treat, disorders such as schizophrenia.
The findings have been peer reviewed and published in the journal The Lancet Psychiatry.
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