Food and Behaviour Research

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29 October 2014 - The Conversation - Mom's prenatal hardship turns baby's genes on and off

Suzanne King, Full Professor of Psychiatry at McGill University
The challenging conditions left in an ice storm's wake provided the unusual opportunity to study prenatal stress prospectively

In January 1998 five days of freezing rain collapsed the electrical grid of the Canadian province of Québec. The storm left more than 3 million people without electricity for anywhere from a few hours to 45 days – one of the worst natural disasters in Canadian history.

The challenging conditions left in the ice storm’s wake provided the unusual opportunity to study prenatal stress prospectively. Living without electricity in the middle of the Canadian winter would stress plenty of pregnant women. Instead of looking backwards, we could track effects of stress going forward in time.

So in June 1998 we recruited nearly 200 women who were pregnant during the ice storm. We sent them questionnaires to measure the objective severity of the hardship they experienced (days without electricity, financial loss, injuries, moving house and so on), and also how much subjective distress they were still feeling from the disaster.

Since then, we have seen that a mother’s level of objective hardship predicts many outcomes: the more days she was without electricity, for example, the lower the child’s IQ, the greater the child’s risk of becoming obese, and the more insulin the child secreted in a glucose tolerance test, which might set him up to develop diabetes later in life.

The big surprise was that the mother’s subjective experience of distress had no effect on any of these outcomes.

We were perplexed: how is it that a child whose mother stayed calm and collected during the ice storm despite losing power for weeks could have worse outcomes than one whose mother was clearly distraught by the ice storm but never lost power? Our study showed it was happening, but how could objective maternal hardship – independent of subjective stress – affect these biological mechanisms? To investigate, my colleague Dr. Moshe Szyf and I started to look at the epigenetics of the ice storm kids.

Though small, our study showed the 1998 ice storm created sufficient hardship for pregnant women that it caused epigenetic changes in their unborn children that have lasted at least 13 years – that’s pretty permanent! No other study had previously shown epigenetic effects linked to objective hardship rather than subjective distress.

The objective severity of the mothers' hardship most affected the methylation of two kinds of genes in the ice storm kids: immune system genes, which might increase risk for asthma and allergies, and metabolism genes, which might affect risk of obesity or diabetes. Our next challenge is to figure out how these epigenetic changes actually affect the children’s health. And a remaining big question is how did the mothers' experiences produce these altered patterns of gene expression?