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Monday, 3 September, 2001, 12:24 GMT 13:24 UK
Social stress 'can kill'
Stressed mice were more vulnerable to the effects of a bacterial infection
Social stress can trigger potentially deadly over-activity by the immune system, scientists have found.

Although the research was carried out on mice, the US scientists believe the results could be directly relevant to humans.

They found that stressful social interactions stimulated a dangerous inflammatory response in the mice equivalent to the human condition septic shock.

Chronic social stress could put these folks at increased susceptibility to inflammatory diseases including septic shock

Dr Ning Quan
The mice were put into either "social stress" or a "physical restraint" groups.

In the first, subordinate mice were placed in a cage with an aggressive dominant mouse for two hours a day.

Mice from the second group were confined in a cylindrical tube for 16 hours without access to food or water.

When the mice were exposed to a bacterial toxin the socially stressed animals were twice as likely to die as those suffering physical hardship.


The stressed mice were found to produce high levels of chemicals called cytokines.

These chemicals regulate the functioning of the immune system. However, they can stimulate inflammation.

Not only were cytokines higher in the stressed mice, the chemicals seemed to be resistant to the effect of other hormones called glucocorticoids, which normally keep inflammation in check.

The result was a mouse equivalent of septic shock - a deadly disorder characterised by a severe fall in blood pressure and widespread damage to body tissues.

Researcher Dr Ning Quan, from Ohio State University in Columbus, said: "During infection, there is a balancing act of the immune system. You want inflammatory cells to kill the bacteria at the site, but you don't want too many at the site.

"Septic shock is directly association with over-inflammation. Sometimes it's not the infection itself that kills a person; rather, it's that the body doesn't properly respond to inflammation."

Doctors had noted glucocorticoid resistance in people who were suffering from major depression or infected with HIV.

Dr Quan said: "Chronic social stress in these patients may contribute to the development of glucocorticoid resistance, which could put these folks at increased susceptibility to inflammatory diseases including septic shock."

The research is published in the Journal of Neuroimmunology.

See also:

25 Jun 01 | Health
Stress: The effects
12 Feb 01 | Health
Breakthrough on killer infection
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