Now a new body of research is challenging that notion. Some scientists posit that what matters is not just the level of stress, or even its type, but how it is thought about. The same stress, perceived differently, can trigger different physical responses, with differing consequences in turn for both performance and health.
Recognising that stress can be beneficial seems to help in two main ways. People who have a more positive view of stress are more likely to behave in a constructive way：a study by Alia Crum of Stanford University's Mind and Body Lab and others found that students who believed stress enhances performance were more likely to ask for detailed feedback after an uncomfortable public-speaking exercise. And seeing stressors as challenges rather than threats invites physiological responses that improve thinking and cause less physical wear and tear.
Humans can respond to stress in several different ways. The best-known is the “fight or flight” response, which evolved as response to sudden danger. The heart rate increases；the veins constrict to limit the bleeding that might follow a brawl and send more blood to the muscles；and the brain focuses on the big picture, with details blurred.
In less extreme situations, the body and brain should react somewhat differently. When people perceive they are being challenged rather than threatened, the heart still beats faster and adrenalin still surges, but the brain is sharper and the body releases a different mix of stress hormones, which aid in recovery and learning. The blood vessels remain more open and the immune system reacts differently, too. Sometimes, though, the wrong response is triggered, and people sitting exams, giving a speech or pitching a business plan react as if to a sudden threat, with negative consequences for both their performance and their long-term health.
Ms Crum believes that attitudes and beliefs shape the physical response to stress. In 2013 she subjected student volunteers to fake job interviews. Beforehand, they were shown one of two videos. The first extolled the way stress can improve performance and forge social connections；the second emphasised its dangers. In the fake interviews, the participants were subjected to biting criticism. When Ms Crum took saliva samples at the end of the study, she found that those who watched the upbeat video had released more DHEA, a hormone associated with brain growth.
In an earlier study Ms Crum and Shawn Achor, the author of “The Happiness Advantage”, visited UBS, an investment bank, at the height of the financial crisis in 2008. They split around 400 bankers into three groups. The first watched a video that reinforced notions of stress as toxic, the second watched one highlighting that stress could enhance performance and the third watched no clip at all. A week later the second group reported greater focus, higher engagement and fewer health problems than before；the other two groups reported no changes.
Other scientists have shown that recognising the benefits of stress can cause measurable improvements in performance. In one experiment Jeremy Jamieson, a psychology professor at the University of Rochester, gathered college students preparing for the Graduate Record Examination (GRE), an entrance test for postgraduate courses. He collected saliva from each of the students to measure their baseline stress response and divided them into two groups. One group was told that stress during practice exams was natural and can boost performance；the other got no such pep talk. The students who received the mindset intervention went on to score higher on a GRE practice test than those who did not. When Mr Jamieson collected their saliva after the exam, it suggested his intervention had not soothed their nerves：they were at least as stressed as those in the control group. A few months later the students reported their scores on the real GRE exam：those who had been
taught to see stress as positive still scored better.
“Google images of stress and you'll see a guy with his head on fire. We've internalised that idea,” says Mr Achor. He instead compares stress to going to the gym. You only get stronger if you push yourself beyond what feels easy, but afterwards you need to recover. The analogy suggests that stress at work may bo performance enhancing, but should be followed by rest, whether that means not checking e-mails on weekends, taking more holiday or going for a strolling in the middle of the day.
Kelly McGonigal, a psychologist at Stanford University and the author of “The Upside of Stress”, helps people rethink stress by telling them to make two lists：of things that stress them；and of things that matter to them. “People realise that if they eliminated all stress their lives would not have much meaning,” she says. “We need to give up the fantasy that you can have everything you want without stress.”
By changing how their bodies process stress and how they behave, such as reframing may help people live healthier lives. In 2012 a group of scientists in America looked back at the 1998 National Health Interview Survey, which included questions about how much stress the 30,000 participants had experienced in the previous year and whether they believed stress harmed their health. Next, they pored over mortality records to find out which respondent died. They found that those who both reported high stress and believed it was harming their health had a 43% higher risk of premature death. Those who reported high stress but did not believe it was hurting them were less likely to die early than who reported little stress.
The study shows correlation, not causation. But since much stress is unavoidable, working out how to harness it may be wiser than fruitless attempts to banish it.
