Stress boosts immunity, but only in the short term

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Stress boosts immunity, but only in the short term

Last Updated: 2004-07-09 13:11:34 -0400 (Reuters Health)

By Alison McCook

NEW YORK (Reuters Health) - A short burst of stress appears to help the

body fight off infections, but chronic stress may produce the opposite

effect, according to a new report.

After reviewing 300 studies that investigated the link between stress

and immunity, researchers found that short-term stress appears to rev up

the immune system, while chronic stress produces changes in the body

that seem to diminish immune functioning.

So are people who are under stress for months at a time -- a result of

unemployment, for instance -- more prone to illness? Unfortunately, more

research is needed to before researchers can make that conclusion, study

author Dr. Suzanne C. Segerstrom cautioned.

This question is " not easy to answer from this body of research, " she

said.

Segerstrom and her co-author, Dr. , based their report on

a review of 293 studies conducted between 1960 and 2001, in which almost

19,000 people took part.

The researcher, who is based at the University of Kentucky in Lexington,

explained that when we are stressed, our bodies release stress hormones,

such as adrenaline and cortisol. When these hormones are intermittently

present during brief periods of stress, they cause the body to release

immune cells capable of quickly and efficiently fighting off infections.

" In essence, you're getting 'first responders' on the scene, in case

something happens, " Segerstrom told Reuters Health.

However, the picture is quite different once those stress hormones are

present for prolonged periods, the authors report in the journal

Psychological Bulletin.

Segerstrom explained that our bodies carry immune cells that respond

only to specific triggers, such as one virus or bacterium. We don't have

enough room to carry legions of each type of these cells, so when a

particular trigger is present, the cell that targets that trigger makes

multiple copies of itself and responds.

However, when people are under prolonged periods of stress, these

trigger-specific cells don't multiply as well, thereby reducing their

ability to fight the triggers, she said.

In an interview, Segerstrom explained that it makes sense that humans

would develop a system that enables their bodies to fight off infections

during short bursts of stress. When early humans were running from

danger, for instance, they were more likely to get injured and a

subsequent infection, and that short-term boosting of their immune

system was likely a good source of protection, she said.

However, the change in immune system functioning with long-term stress

" does not make as much sense, " she said, and is likely an " unintended

consequence " of chronic stress, which is relatively new, in evolutionary

terms.

Long-term stress, such as from unemployment or poverty, " was just not

characteristic of the kinds of things people experienced, until very

recently, " said Segerstrom.

SOURCE: Psychological Bulletin, July 2004.

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Mayo Clinic in Rochester

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s Hopkins Medicine

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