Early stress is contagious in adulthood

A zebra finch’s tough childhood shortens both its life and its mate’s

Among the regrettable things one might catch from a long-term mating partner, add the life-shortening effects of stress in childhood.

GHOST STRESS Even if zebra finches look healthy and live in a safe place, a stressful chickhood for one mate in the pair raises both birds’ risk of a shortened life span. Juniors Bildarchiv / Alamy

Chickhood stress is bad for zebra finches. Nestlings dosed with stress hormones tend to die earlier in adulthood even if they enjoy plentiful food in predator-free lab quarters after maturity.

And so do those unfortunate nestlings’ mates, a new study finds. Zebra finches, which form strong pair bonds, somehow manage to transmit their own risks of stress-shortened life span to their partners.

“It’s like giving them a disease,” says evolutionary ecologist Pat Monaghan of the University of Glasgow in Scotland.

Working out the effects of early stress over a lifetime requires lab experiments, because most natural exposures to stress usually continue into adulthood. So Monaghan and her colleagues administered stress hormones to chicks for about half of their month or so as nestlings and gauged the long-term effects on the treated birds and their mates.

After three years, the researchers found, about 20 percent of finches stressed with hormone spikes as nestlings had died — and so had about the same proportion of their mates who had enjoyed tranquil chickhoods. In contrast, only about 5 percent of finches with happy childhoods who were mated to other easy-childhood birds had died.

The shorter life spans for survivors of early stress aren’t a surprise, but the transmission to partners is, says Jonathan Seckl of the University of Edinburgh, who studies stress hormones. “If this was true in humans, such folks should carry a health warning,” he says.

Worst off were birds from rough backgrounds mated to each other: About 40 percent of them were dead in three years, the researchers report in an upcoming Proceedings of the Royal Society B.

“The effect [Monaghan and colleagues] have demonstrated illustrates just how much your partner can affect your own health, even in very subtle ways,” says Simon Griffith of Macquarie University in Sydney. Shortening the partner’s life didn’t seem to come from having to work harder to make up for a mate that wouldn’t or couldn’t put in its own effort, but from some less direct effect.

“If these data can be applied to humans at all,” says Michael Romero of Tufts University in Medford, Mass., “the take-home lesson would be to choose your mate well so that your mate can help decrease — somewhat — the number of stressors that life throws at you.”

Life with a survivor of childhood stress may just be stressful, Monaghan speculates. The traumatized bird may not be able to provide the normal comfort that the birds find in familiar company, an effect called social buffering. Or the trauma survivor, stuck with a lifelong tendency for strong and prolonged responses to real or perceived threats, may become a source of stress in its own right.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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