Famine during pregnancy doubles risk of mental illness.
Babies born to malnourished mothers are twice as likely to develop schizophrenia, according to new research.
The link could help researchers unpick the causes of schizophrenia, a socially disabling mental disorder with no known cause or cure. Most agree it is likely to have both genetic and environmental triggers.
Researchers first saw a link between schizophrenia and hunger when investigating the Dutch 'hunger winter' of 1944-45, when the Nazis blocked food supplies to much of the Netherlands. Babies born that year were twice as likely to become schizophrenic, according to a 1992 study1. But as only 25 people in the sample were diagnosed with the illness, the result could have been a statistical fluke.
Now another famine, halfway across the world, has lent support to the link between famine and schizophrenia.
In China around 1960, a combination of bad weather and Mao Zedong's Great Leap Forward - in which farmland became industrial, and ineffective new agriculture was tried - plunged the country into famine. One of the hardest-hit areas was Anhui province in 1959-61. The researchers selected one area in that province and gathered data from the local psychiatric hospital.
A critical deficiency
Neuroscientist David St Clair of the University of Aberdeen in Scotland and his team looked at medical records from the area from 1956 to 1965. Just as in the Netherlands, the risk of children developing schizophrenia doubled during the famine years: hundreds of children per year were later diagnosed with the disease, putting their risk at 2%, compared to 1% for children born in easier times. The finding appears in this week's Journal of the American Medical Association2.
The finding is unlikely to much affect the total number of schizophrenics, the researchers note, as fewer babies overall survive during famines.
Feng Zhang, also from the University of Aberdeen and one of the study's authors, says that although the link between malnurishment in the womb and schizophrenia is clear, the mechanism by which they are related is still unknown. "Nobody knows what is going on, but we are beginning to think of it as a gene-environment interaction."
Researchers including Ezra Susser, who conducted the Dutch study, are working to discover the cause. One popular idea is that a deficiency of folic acid is to blame. Lack of this nutrient, found in leafy greens and some vitamin supplements, is also implicated in developmental defects in the baby's spinal cord. Researchers are looking at genes for folic acid metabolism and how these might relate to mental illness.
Susser, a psychiatrist and epidemiologist at Columbia University and the New York State Psychiatric Institute (NYSPI), says he is glad to have his findings supported. It is difficult, he notes, to find natural experiments in which to conduct such studies, as the famines must be at least 40 years old in order to give schizophrenia a chance to develop.
"Epidemiologists and medical researchers can take satisfaction in the fact that they can take something so catastrophic and wring from it scientific knowledge that would otherwise be unavailable," says Richard Neugebauer, also of the NYSPI. "Wonderful as that is, lets none of us forget that we should be active in the present to prevent further catastrophes."
SusserE. & LinS.Arch Gen Psychiatry, 49. 983 - 988 (1992).
St ClairD. & et al. Am. Med. Assoc., 294. 557 - 562 (2005).