"Humans should not try to avoid stress any more than they would  _ food, love or exercise," said Dr. Hans Selye, the first physician to document the effects of stress on the body. While here's on question that continuous stress is harmful, several studies suggest that challenging situations in which you're able to rise to the occasion can be good for you. In a study of 158 hospital nurses, those who faced considerable work demands but deal with the challenge were more likely to say they were in good health than those who felt they couldn't get the job done.  Stress that you can manage also promote immune function.  In a study at the Academic Center for Dentistry inprefix = st1 /Amsterdam, researchers put volunteers through two stressful experiences. In the first, a timed task that required memorizing a list followed by a short test, subjects believed they had control over the outcome. In the second, they weren't in control. They had to sit through a bloody video on surgical procedures. Those who did the memory test had an increase levels of immunoglobulin A, an antibody that's the body's first line of defense against germs.  However, the video-watchers experienced a fall in the antibody. Stress encourage body to produce certain stress hormones .  In short bursts these hormones have a positive effect, including improved memory function. "They can help nerve cells handle information and put it into storage," says Dr. Bruce McEwen of Rockefeller University inNew York. But in the long run these hormones can have a harmful effect on the body and brain. "Continuous stress is not good for you," says Richard Morimoto, a researcher at Northwestern University in Illinoisstudying the effects of stress on one's life, "It's the occasional burst of stress or brief experience of stress that could be protective. " The passage is mainly about  _  .
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