Vitamin D deficiency at birth linked to schizophrenia
Vitamin D deficiency at birth is associated with a significantly increased risk of schizophrenia, according to a new study, confirming a potential way to prevent the disease in the future.
Researcher Professor McGrath, from UQ’s Queensland Brain Institute, told doctorportal: “it’s very unusual that we find risk factors that are so readily treated by safe, cheap and publically accessible interventions.”
“Obviously it’s not a done deal yet. It’s a correlational study and randomised controlled trials need to be done. But we feel we need to keep chasing down this hypothesis.”
The case-controlled study, published in Scientific Reports, included 2602 participants. They were randomly selected from all infants born in Denmark between 1981 and 2000, who received a diagnosis of schizophrenia.
Controls, drawn from the same birth cohort, were individually matched on sex, date of birth and were alive and free of schizophrenia at the time of onset of the matched case. The concentration of 25 hydroxyvitamin D (25OHD) was assessed from neonatal dried blood samples, which have been collected and systematically stored since 1981.
The researchers found that those with 25OHD below 20.4 nmol/L (consistent with standard definitions of vitamin D deficiency) had a 44% increased risk of schizophrenia compared to those in the reference category.
Unlocking an enduring mystery around schizophrenia
Professor McGrath said that researchers have known for a long time – since around 1920 – that people born in winter have a slightly increased risk of developing schizophrenia than those born in other seasons.
“This has always been a bit of mystery. People thought it might have been due to infection and other factors, but we proposed it could be vitamin D, which is mostly known to be linked to bone health.”
Professor McGrath said that most of the work done at the Queensland Brain Institute has demonstrated that if vitamin D is removed from animal models, brain development will be altered.
“That was the hypothesis, so we needed to find a sample. Fortunately, our colleagues in Denmark have access to a biobank, and in 2010 we did a study with this and showed that vitamin D deficiency at birth was linked to an increased risk of schizophrenia.”
“In this new paper, we’ve looked at the research question in a much bigger sample of 2602 and we’ve found exactly the same thing – that babies who have vitamin D deficiency at birth have a 44% increased risk of schizophrenia.
Biological mechanism behind the association is complex and still being probed
“Vitamin D is related to steroid hormones, and we know that if you have steroid hormones you reduce the rate of cell division and you drive cell differentiation.”
New emerging theories relate to the common genetic variants in calcium pathways, which have been shown to increase schizophrenia risk.
“It turns out that vitamin D in many areas of the body, including the brain, alters these exact same channels and we’re exploring that question currently”, Professor McGrath said.
“The problem with vitamin D is that it is one of those hormones which does lots of things to lots of different tissues, so we’ve got a very big sandpit to play in and it will be a challenge to sort out what the mechanisms are.”
Research to tease out a link between vitamin D and other brain disorders
Professor McGrath studies an active area of research: “We have funding from a Danish research agency to measure vitamin D in a very large sample of 80,000 babies and we’ve started that now in Copenhagen, and it will be about two years before those results are ready.”
“We’re looking at whether low vitamin D impacts on other brain disorders. We’ve done some work in the Netherlands a couple of years ago where we measured vitamin D in maternal sera that was taken at 20 weeks of gestation.”
This large study showed that for mothers who had low vitamin D during mid-gestation, their offspring had an increased risk of autism and related symptoms at age 6.
“So we’re wondering whether vitamin D deficiency is just bad for brain development,” Professor McGrath said.
“Most kids that are exposed to vitamin D deficiency are fine – they might have weak bones but most don’t get mental illness. However, we have not been able to reject the hypothesis yet based on epidemiology.”