Do you ever experience stress? Of course you doÂ—who doesnÂ’t? IÂ’ll bet you define stress as the pressures that life places on you, and you think that stress is bad for you. Scientists who study stress have a more complex view of what stress is, and whether it is bad for you.
Dr. Bruce McEwen at Rockefeller University in New York City is one of the best known stress researchers. How does he define stress? He would ask you to compare yourself to one of your ancestors, maybe someone who lived 10,000 years ago on the Serengeti desert in Africa. What did your ancestor have to worry about? Eating, and being eaten, would top the list. While fruits and vegetables were not that hard to find, humans only succeeded in finding a meal of meat every few days. Water, too, could be scarce. And your ancestor knew that he or she might be attacked and killed by a large, wild animal, or by another human.
Suppose your ancestor saw a lion approaching. To have a chance of escaping, what would your ancestor need? For one thing, she would need her wits about her: A person needs to think fast and clearly in a crisis. For another, sheÂ’d need all of her muscles to be as strong as possibleÂ—to run as fast as possible, and to fight if that was necessary. To get the best work out of the muscles, they would need a maximum amount of fuelÂ—oxygen and sugar. For an immediate surge of oxygen, the heart and lungs need to suddenly work very hard. For an immediate surge of sugar, your ancestor would need certain hormones to liberate sugar from the carbohydrates stored in the body. And in case your ancestor was injured, her blood vessels would need to tighten to minimize blood loss and her immune system would need to be stimulated to fight any infection of the injured tissue.
The body has a systemÂ—called the stress response, the Â“fight-or-flight response,Â” or, more recently, allostasisÂ—that achieves all these things. When the brain perceives a threat like an approaching lion, it generates brain hormones and neurotransmitters that do all of these things. The stress response continues until the threat has passed. McEwen defines stress as the brainÂ’s perception of a vital threat, and the stress response is the bodyÂ’s reaction to that stress. Whether the stress response is good or bad for you depends on the circumstances.
While you probably have never faced a lion on the Serengeti, you may occasionally have faced a sudden threat: A tree thatÂ’s hard to avoid hitting while skiing, or an automobile that runs a red light and nearly hits you. The stress response was there for you, and it may well have led your activated brain and body to take action that protected you. So the stress response, in such circumstances, is very good for you.
But the stress response can be bad for you when it keeps being turned on repeatedly throughout the day, every day. Another way of looking at how your life today is different from the life of your ancestor on the Serengeti, consider what your ancestor did not have to worry about: The increased cost of health insurance next year, the drop in the stock market today, the 50 e-mail messages that have gone unanswered since breakfast, and the front page news story about how a new epidemic of bird flu could kill millions of people.
Our ancestors lived from crisis to crisis, but the long periods in between were relatively tranquil. Their stress response was turned on only intermittently. Today, we are constantly barraged with things to worry about and our stress response is turned on most of the day. Yet it canÂ’t help us to deal with the things that turned it on. It wonÂ’t make the stock market go back up, or prevent the epidemic of bird flu. It just churns away, doing nothing but causing trouble.
When itÂ’s constantly turned on, the stress response can have unhealthy effects on the body. It can contribute to heart troubles, it can make the immune system less effective in warding off infections, it can even cause the cells in our body to age more quickly. And when our cells age more quickly, so do we.
So what can we do about chronic stressÂ—the bad kind of stress? Stress management techniques like meditation and yoga can help quiet the stress response. And a healthy lifestyleÂ—particularly eating healthy and exercising regularlyÂ—actually fight against all the unhealthy effects of chronic stress. So even if we donÂ’t use stress management techniques to quiet the stress response, a healthy lifestyle can help counter the unhealthy effects of stress. ItÂ’s very hard to escape the constant stressors that surround us, but we can protect ourselves against the effects they have on our body.
This year has been especially stressful for a lot of people. How are you handling the chronic stress that gets heightened when times are tougher?
Anthony Komaroff, M.D., is the Simcox-Clifford-Higby professor of medicine at Harvard Medical School (HMS), and editor-in-chief of Harvard Health Publications at HMS. He is a practicing senior physician and was formerly director of the Division of General Medicine at Brigham and Women's Hospital.
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