Brief episodes of stress could be good for us, protecting us from the effects of ageing ? as long as we're not too frazzled to begin with. That's the surprise finding of a study measuring stress-related damage inside cells.
Chronic stress causes wear and tear to body tissues, increasing our risk of developing age-related diseases such as cancer, diabetes and dementia.
One reason for this is that the body responds to stress by burning fuel to release energy. While this helps us respond to a threat, it also swamps cells with toxic free radicals produced during metabolism. Switched on long-term, this response damages DNA, RNA and other molecules, ageing us before our time.
Kirstin Aschbacher of the University of California, San Francisco, and her colleagues wanted to test whether a short period of intense stress is more damaging if we are already living through a stressful period. They took a group of women chronically stressed by caring for close relatives with dementia, and made them give a speech in front of a sceptical panel of judges. A group of unstressed women performed the same task to act as a control group.
The researchers asked the women to say how stressful they found the test. They also measured their levels of the stress hormone cortisol, plus biochemical markers of damage inside their cells.
Unexpected effect
For the stressed women, the extra challenge indeed proved particularly harmful: the threat of the test caused more cellular damage than in the non-stressed controls. Perhaps more intriguing, though, was an unexpected effect Aschbacher and her colleagues found within the control group.
Among these normally relaxed women, those who found the task moderately stressful had lower levels of cellular damage than those who did not find it stressful at all. In other words, while chronic stress can have knock-on effects that damage cellular structures, short bursts of stress can reduce such damage and protect our health in some circumstances.
The idea that being under pressure helps to focus attention and makes us better at cognitive tasks has been around for almosta century. But Aschbacher's study is a first step to showing how it can sometimes make us physically healthier as well ? although exactly what is going on at the cellular level to explain the result is still unclear.
"It's like weightlifting, where we build muscles over time," says Aschbacher. As long as there is time to recover in between, short bursts of psychological stress "might allow us to become stronger".
Bruce McEwen, who studies the physiology of stress at the Rockefeller University in New York City, describes the research as "provocative", and says it is starting to untangle the mechanisms by which stress can have positive effects. "Mother Nature put these things there to help us adapt and survive," he says.
Journal reference: Psychoneuroendocrinology, doi.org/mb5
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