Aug 28, 2012 by EDITOR
Shorts Bursts of Mild Stress Are Actually Good For The Body And Immune System
Stress is bad for you -- you've heard this a million times. But it can be good for your immune system if it's short-term, says a study.
What doesn't kill you only makes you stronger, or so the saying goes.
Short-term stress, the fight-or-flight response, a mobilization of bodily resources lasting minutes or hours in response to immediate threats, stimulates immune activity, said Firdaus Dhabhar, associate professor of psychiatry and behavioural sciences and member of the Stanford University Institute for Immunity, Transplantation, and Infection.
And that's a good thing. The immune system is crucial for wound healing and preventing or fighting infection, and both wounds and infections are common risks during chases, escapes and combat, the Journal of Psychoneuroendocrinology reported.
Experiencing chronic stress day after day can produce wear and tear on the body physically and mentally, and can have a detrimental effect on learning and emotion. However, acute stress has a different effect.
Working with colleagues at Stanford and two other universities, Dhabhar showed that subjecting lab rats to mild stress caused a massive mobilization of several key types of immune cells into the bloodstream and then onto the skin and other tissues, according to a university statement.
Researchers at the University at Buffalo have previously shown, in trials using rodents as an animal model, that acute stress can produce a beneficial effect on learning and memory, through the effect of the stress hormone corticosterone (cortisol in humans) on the brain's prefrontal cortex, a key region that controls learning and emotion.
Stanford researchers found that the large-scale migration of immune cells, which took place over two hours, was comparable to the mustering of troops in a crisis, Dhabhar said. He and his colleagues had previously shown that a similar immune-cell redistribution in patients experiencing the short-term stress of surgery predicts enhanced postoperative recovery.
Chronic stress suppresses the transmission of glutamate in the prefrontal cortex of male rodents, which is opposite to the facilitating effect of acute stress, and that estrogen receptors in female rodents make them more resilient to chronic stress than male rats.
Investigators were able to show that the massive redistribution of immune cells throughout the body was orchestrated by three hormones released by the adrenal glands, in different amounts and at different times, in response to the stress-inducing event. These hormones are the brain's call-to-arms to the rest of the body, Dhabhar said.
"Mother Nature gave us the fight-or-flight stress response to help us, not to kill us," said Dhabhar, who has been conducting experiments for well over a decade on the effects of the major stress hormones on the immune system.
The findings paint a clearer picture of exactly how the mind influences immune activity. "An impala's immune system has no way of knowing that a lion is lurking in the grass and is about to pounce, but its brain does," Dhabhar added.