Striking new studies reveal why you should embrace the benefits of short bouts of stress. Discover how this new research may change your views on stress.
A glance at the clock tells you you’re going to be late for that big meeting. You can feel your blood pressure rise and hear your rapid pulse thrumming in your ears. Then you remember something you read about the dangers of stress—that it can harden arteries, kill brain cells, trigger tumours. Now you’re stressed about stress itself.
If this sounds familiar, you’re not alone. According to a 2013 survey, the average stress level among American adults is 5.1 on a scale of ten; that’s one-and-a-half points above what the respondents judged to be healthy.
"Short bouts of everyday stress can actually be a good thing"
“Stress has a very bad reputation,” acknowledges Firdaus Dhabhar, associate professor of psychiatry and behavioral science at Stanford University, California. “And justifiably so,” he adds.
Much of what we know about the physical and mental toll of chronic stress stems from the late 1970s. Hormones released during the fight-or-flight response—the ones that helped our ancestors avoid becoming dinner—have detrimental effects when the stress is severe and sustained. Chronic exposure to one of these hormones, cortisol, causes brain changes that make it increasingly difficult to shut the stress response down.
But take heart: recent research paints a different portrait of stress, one in which it has a positive side. Situations we typically perceive as stressful—a confrontation with a colleague, the pressure to perform, a to-do list that’s too long—are not the toxic type of stress that’s been linked to serious health issues. Short bouts of this sort of everyday stress can actually be a good thing.
When Firdaus Dhabhar was starting his graduate work at Rockefeller University, New York, in the early 1990s, “the absolutely overwhelming dogma was that stress suppresses immunity”. But this didn’t make sense to him from an evolutionary perspective. If a lion is chasing you, he reasoned, your immune system should be ramping up, readying itself to heal torn flesh. It occurred to Dhabhar that the effects of acute stress, which can last minutes to hours, might differ from the effects of chronic stress, which last days to years.
Dhabhar likens the body’s immune cells to soldiers. Because their levels in the blood plummet during acute stress, “people used to say, ‘See, stress is bad for you; your immune system’s depressed,’ ” he says. “But most immune battles are not going to be fought in the blood.” He suspected that the immune cells were instead travelling to the body’s “battlefields”—sites most likely to be wounded in an attack, such as the skin, gut and lungs.
In studies where rats were briefly confined (a short-term stressor), he showed that after an initial surge of immune cells into the bloodstream, they quickly exited the blood and took up positions where he predicted they would.
This strategic deployment of immune cells can speed wound healing, enhance vaccine effectiveness and potentially fight cancer. In 2009, Dhabhar’s team showed that knee-surgery patients with robust immune redistribution recovered significantly faster and had better knee function a year later than those with a more sluggish immune mobilisation.
In other studies, volunteers who exercised or took a maths test (both acute stressors) immediately prior to being vaccinated had a heightened antibody response relative to volunteers who sat quietly.
Dhabhar thinks the key to maximising the benefits of stress while minimising any negative effects is interspersing “regular hits” of acute stress with periods of low or no stress—what he calls “green zones”. That doesn’t mean you have to add bungee jumping to your daily routine; rather, he advises harnessing the daily aggravations that life already throws at you. And exercising more. Exercise is widely touted as a stress reliever, but it’s also a short-term stressor, he says. “Exercise activates the same biological response as seeing a predator or making a speech.”
Whereas chronic stress shrinks the hippocampus (one of the brain’s key memory centres), impairs cognitive function and even increases risk of mental illness, short bursts of stress can enhance memory and learning. Conor Liston, an assistant professor of Neuroscience at Cornell University, New York, says, “If you think of stress in terms of arousal—being awake and alert and oriented to changes in the environment—this is a good thing for learning.”
Under certain conditions, the stress hormone cortisol appears to boost the brain’s receptivity to learning, what neuroscientists call “brain plasticity”. Neurons in the brain each form thousands of synapses—structures that they use to communicate with other neurons. As learning occurs, new synapses sprout and old ones are pruned.
When Liston experimentally depleted corticosterone (the mouse equivalent of cortisol) in a group of rodents, synapse turnover—a marker of brain plasticity—ground to a halt. In this state, the mice were unable to learn a new skill. Conversely, when Liston gave another group of mice a low-dose shot of corticosterone, the rate of synapse turnover doubled.
There’s a danger in leaving the dial turned up for too long, though. When Liston exposed mice to high-dose corticosterone for ten days, the animals experienced a net loss of synapses. It turned out that pruning outpaced synapse formation, which may help explain the effects of chronic stress on mental functions.
The point at which stress turns toxic is when it becomes unrelenting and traumatic, and when sufferers lack control and social support.
“What we tend to mean when we talk about stress are the daily experiences of time scarcity, role uncertainty, social conflict and pressure,” says Kelly McGonigal,
a health psychologist, author and Stanford lecturer. “The type of ‘stress’ that’s toxic has more to do with social status, social isolation and social rejection.”
High-ranking individuals may have demanding jobs, but they also enjoy a greater sense of autonomy. In a 2012 study, researchers found that a group of leaders military officers and government officials—had lower levels of cortisol and anxiety than a comparable group of non-leaders. This is despite the fact that leaders appeared more taxed: they slept significantly fewer hours per night than non-leaders. Among those the leaders, those who managed more people and had more authority also had lower cortisol levels and lower anxiety than those with less clout.
“The type of ‘stress’ that’s toxic has more to do with social status, social isolation and social rejection”
Given the prevelance of the messaging suggesting that any form of stress is bad, McGonigal worries that fear may lead people to avoid exactly the kinds of stressful experiences that are critical for health and longevity. “We know that having a meaningful job and social connection are protective; we also know that mastery of challenges is protective.”
Additionally, how people view stress—as a threat versus an opportunity—can alter their physiologic responses to it. In a 2011 study, volunteers were exposed to positive messages about stress prior to a public-speaking task. Their hearts pumped more efficiently and their blood vessels constricted less during the stressor than controls who were given no information.
In her lectures and classes, McGonigal used to teach people how to reduce or cope with stress, as if it were something to be avoided and dreaded. But in light of this research, she’s changed her tune. Instead, she encourages them to harness the stress. “Rather than trying to slow your pounding heart, why couldn’t you view it as your body giving you energy?” she says.
After all, even if you could live in a stress-free bubble, you’d probably have to excise all the things that imbue your existence with happiness and meaning—like relationships, challenging work, learning and growth. “In a way,” McGonigal concludes, “stress is a kind of engagement with life.”
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