Stressed out?

Could back-to-school jitters actually be good for you? New research on mice suggests that short-term stress boosts the body's disease-fighting immune system.

To find out how the immune system responds to temporary anxiety, like being frightened, scientists stressed a group of mice by confining them in tight quarters for short periods of time. Afterward, these mice had more germ-killing cells called leukocytes in their skin than mice that hadn't been confined.

Why the difference? Firdaus Dhabhar, the immunologist who led the study at Ohio State University, proposes that short-term stress warns the body of possible injury or infection. In response, the immune system sends leukocytes to areas in the body where injuries are likely to occur.

But don't stress yourself out just to fight off germs: Dhabhar points out that because these studies were done only on mice, the results still need to be tested on people. Plus, studies on humans suggest that long-term stress may cause sleeplessness, depression, or even a weakened immune system.