IT’S one of the stranger sounding ideas in psychiatry—that your chances
of developing schizophrenia depend on how sunny it was months before you were
even born.
But evidence is accumulating to support the theory that vitamin D deficiency
during pregnancy, caused by a lack of sunlight, can alter the development of a
child’s brain in the womb. The data for a link with schizophrenia is still
controversial, but potentially worrying because vitamin D deficiency is so
common.
Vitamin D’s role in building healthy brains had been largely ignored, until
researchers began to spot some curious epidemiological trends. People who
develop schizophrenia in Europe and North America are more likely to be born in
the spring. And they are roughly four times as likely to be born to
Afro-Caribbean immigrants living in England as they are to have parents of other
ethnic origins living in the same areas.
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The body needs sunlight to make vitamin D, and people with darker skin need
more than paler-skinned people. So such observations led John McGrath of the
Queensland Centre for Schizophrenia Research in Wacol to propose that a lack of
vitamin D during early development tips the balance towards schizophrenia in
genetically susceptible people
(91av, 21 July 2001, p 38).
Now McGrath has completed studies on rats that add experimental meat to the
epidemiological bones. With neurobiologist Alan Mackay-Sim of Griffith
University in Queensland, McGrath has found that—just like humans with
schizophrenia—adult rats deprived of vitamin D from conception are more
startled than normal by a loud noise preceded by a soft noise. Ventricles in the
brains of vitamin-deprived baby rats are also unusually large, a feature seen in
people with schizophrenia, they told the International Society for Developmental
Neuroscience meeting in Sydney last week.
The researchers also used “gene chips” to look at the activity of thousands
of genes in the brains of adult rats deprived of vitamin D during gestation. The
chips revealed many genes had become less active, including three for brain
receptors, and several that code for proteins involved in building nerve
synapses.
“It’s an exciting lead,” says Fred Mendelsohn, director of the Howard Florey
Institute for experimental physiology and medicine in Melbourne. But he and
others point out that the new findings are a long way from decisively showing
that a lack of vitamin D during pregnancy helps trigger schizophrenia.
McGrath agrees, but says the rat studies clearly show that too little vitamin
D “does something nasty to the brain”. He argues that we urgently need to find
out exactly what that is, because vitamin D deficiency affects 12 per cent of
women of childbearing age, according to a large US survey.
“This should be a big wake-up call. We should find out quickly because [low
vitamin D] could impact general intelligence, and have a whole range of
neurological outcomes,” says McGrath. But he warns pregnant women not to take
additional vitamin D until more is known about its role in development—too
much of the vitamin may cause birth defects.