by Jo Marchant
When it comes to longer-term health, challenge responses seem to be largely positive, while threat states are more damaging. Mendes has found that people who experience a challenge response bounce back to normal fairly quickly, and a range of studies suggests that mild to moderate bursts of such “positive” stress, with time to relax in between, provides a useful workout for the cardiovascular and immune systems. “In many ways, what we do in these psychologically stressful tasks parallels beautifully what you see in exercise stress,” says Mendes. Just as with physical exercise, if we put our bodies under a manageable amount of stress, then go home and rest, this eventually makes us stronger and more resilient. In essence this is what we’re doing every time we go on a roller coaster, or watch a scary film.
By contrast, people in a threat state take longer to recover to baseline once a task is over, both mentally and physically. They tend to worry more about how they did, and remain more vigilant for future threat. Their blood pressure also stays high. Over time, the extra strain on the heart can lead to hypertension. And as we’ve seen, repeated activation of cortisol can damage the immune system.
Intriguingly, Mendes has found that simply changing how we think about our physical response to stress can have a dramatic effect. She subjected volunteers to a grueling ordeal called the Trier Social Stress Test. It involves 15 minutes of public speaking and mental arithmetic in front of a panel of stern judges, and in lab studies it reliably induces a state of fight or flight.
Mendes told some of the volunteers that experiencing physical symptoms of anxiety during the test, such as a racing heart, was a good sign. It meant that oxygenated blood was being delivered to their brain and muscles, she explained, and would help them to perform better. Remarkably, simply knowing this shifted these volunteers towards a challenge response—with greater vasodilation and cardiac output—compared to a placebo group (advised instead to ignore the source of their stress) and a group who received no instructions at all.42
In another study, Mendes showed that reframing the body’s responses in this way doesn’t just shift volunteers’ physiology, it improves their performance too. She asked students preparing for the Graduate Record Exam (GRE)—a high-stakes test required for admission into graduate school—to take a fake test in the lab. Compared to a control group, those told to interpret their stress as positive had the same physiological benefits as in the previous studies. But they also got higher scores—not just in the fake test but in the real GRE, which they took up to three months later.43 “Of all my 60 or 70 published papers, this is the result that was most surprising for me,” says Mendes. “It was such a tiny mindset change.”
Mendes’s work shows that we don’t have to be ruled by stress. Even with a small shift in attitude, we can start to reduce the health impact of stressful events, and to perform better under pressure. Unfortunately, it’s not always easy just to decide to be less stressed or to think about our problems more positively. People who are chronically stressed, in particular, can become locked into negative patterns of thinking.
That’s because, over time, stress physically rewires our brains.
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ONE NIGHT at teatime, my five-year-old daughter leapt away from her fish fingers with a shout. She pointed to a sizable spider on the wall by her chair, and refused to return until the creature was removed.
This posed a problem for me because I’m scared of spiders. But as the only adult in the house at the time it was up to me to do something about it. And (although I’ve clearly failed so far) I’m trying not to pass on my irrational fear to my daughter. I approached the offending arachnid, armed with a coaster and a plastic cup.
I could feel a fight going on in my mind. On one side was a red, flashing alarm. It contained no words, just deep-seated dread and revulsion. Doing battle with this primitive danger signal was a sensible, soothing voice that insisted everything was fine. These two armies were fighting for control of my body too. One side urged my muscles to freeze, while the other was sending instructions to relax and advance. I duly ejected the spider from the kitchen, but doing it was like moving through treacle.
Most of the time, we maintain the illusion of being a coherent, whole person. But there are certain times, even during everyday experiences like confronting a spider, when the conflicting mechanics of the brain become exposed. When we sense a potential danger, several key brain regions interact to decide what we should do about it. One is the amygdala, a quick response system for detecting threats in the environment. It stores emotional memories, especially distressing ones, and when similar scenarios appear again, it triggers fear, anxiety and the fight-or-flight response. The source of phobias and prejudices, the amygdala works within a heartbeat and involves no conscious thought.
Working against its primitive drives are the hippocampus, which adds factual content to memories, and the prefrontal cortex, which carries out higher cognitive functions, such as planning and rational thought. These work more slowly, but analyze situations more logically to defuse our alarm and turn down our response to fear or stress. Which side ultimately wins determines whether we lash out or speak kindly; whether we run or face our fears. And it turns out that in any particular person’s brain, the odds are stacked in a way that depends on their life experiences, specifically their previous exposure to stress.
In one key experiment, psychologists showed short videos to teenagers at a high school in St. Louis, Missouri. These featured neutral scenarios such as a sales assistant watching a shopper, and the students were asked to imagine themselves in each situation. Most saw nothing untoward, but those from disadvantaged backgrounds (after controlling for race) were much more likely to interpret the scenarios as threatening—thinking they were about to be accused of shoplifting, for example—and they experienced raised heart rates and blood pressure to match.44
This effect appears to last for life—Northwestern’s Greg Miller got the same result when he showed the videos to adults raised in poor or well-off households.45 Similar effects have been seen in caregivers like Lisa, and those who have suffered trauma or abuse in early life. People who are chronically stressed find small hassles much more stressful than normal. And they’re much more likely to experience a threat rather than a challenge response.
Over the last few years, neuroscientists including Bruce McEwen of Rockefeller University in New York have discovered why. In animal experiments as well as in people who are chronically stressed, repeated activation of the amygdala causes it to become bigger and better connected over time, while the hippocampus and prefrontal cortex wither and shrink.46 For example, a study carried out three years after the 9/11 terrorist attacks in New York found reduced gray matter volume in these brain regions in otherwise healthy adults living close to the destroyed buildings.47 This reshaping of the brain has been linked to psychiatric disorders including dementia and depression.
Here, then, is one explanation for how the effects of early adversity can persist throughout a lifetime (we’ll discover another in chapter ten). Stress influences how the brain is wired, making us extra-susceptible to future problems by destroying the very brain pathways that would help us to stay calm and in control.
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AFTER MEETING SUSAN, I head across town to a quiet road marked by a sign: “Milledgeville Housing Authority.” The houses here are small bungalows, each divided into two tiny apartments. I’m struck by how impersonal they are compared to Susan’s home. There are no borders, fences, flowers or garden furniture—just rows of identical brick boxes, evenly spaced on the grass.
I knock on the door of the address I’ve been given and am met by Monica. She takes a while to come to the door but greets me warmly. “I forgot you were coming!” she says. The 39-year-old is wearing a strapless green-and-yellow sundress that leaves the expansive brown flesh of her chest, arms and shoulders to spill over the elastic. Her black hair is set into glossy curls, and when she smiles, a gold tooth flashes.
The front door leads
directly into her living room, a small, square space with bare walls and a vinyl floor. The room is dimly lit—the blinds are closed despite gorgeous sunshine outside—and the only pieces of furniture are a faded blue sofa and chair, a low table and a TV. Despite the ashtray on the table, a few cigarette butts are scattered on the floor. Monica gestures to the sofa and absentmindedly flips on the TV as we sit down to talk.
She tells me that she never graduated from high school and now works in a school cafeteria. She makes a face. “I earn $700 a month,” she says. “A month!” She’s also a single mom to Takisha, who is just home from school, dressed in red T-shirt and black leggings with a red bow in her long, plaited hair. The teenager is tall, but overweight and a little awkward. When instructed by her mother she sits opposite us, tapping buttons on her phone.
One of Monica’s biggest worries is keeping her daughter safe, she tells me: “I don’t let her go anywhere.” Takisha is just 13, but already other kids in her class are smoking, drinking and having sex.
Monica recalls her own teenage years, including one evening when a close girlfriend invited her out. She didn’t trust the other girl who was to join them, so she declined. “The next day I heard they were locked up for robbery. They poured hot grease on this elderly guy and robbed him,” she says. “Suppose I’d been in the car! One bad decision and that will change your whole life.” So far, though, Takisha has stayed out of trouble and gets good grades in school (at one point in our conversation, she casually quotes in Latin), and she tells me she’d like to be a pediatrician when she grows up.
The pair clearly have a close relationship: they gently tease each other, and Takisha looks shyly towards her mother for approval before she speaks, for example when I ask how she spends her time. There isn’t much to do in Milledgeville, it seems. “I like being on my phone,” she says. “I like eating.” Monica’s answer is similar. The pleasures in her life are TV—she mostly watches talk shows, and documentaries featuring real-life stories, for example one about a teenager who hanged herself after being bullied online—and food. Takisha would eat healthy foods if she got the chance, says Monica, such as oatmeal, yogurt or salad. “But I don’t eat it, so I don’t buy it.”
Instead, she finds comfort in chicken wings and other fried foods. “We are living in poverty,” she says. “I turn to food. That is my everything. I hate it, but to drown out my issues and my stress I eat.”
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MONICA AND TAKISHA aren’t alone. In many different countries, scientists have found that people brought up in poverty are more likely to smoke and drink excessively and less likely to exercise. They eat unhealthy diets, and women are more likely to be obese.48 As well as damaging health directly, these behaviors also make inflammation worse: smoking and a high-fat diet are both associated with higher inflammation, for example, while regular exercise can reduce it.
Why do people in poor communities behave differently? There are plenty of practical reasons: fresh vegetables and gym membership don’t come cheap. There’s also strong peer pressure to make bad life decisions; Monica has good cause to keep Takisha indoors even though that impacts her daughter’s health. And for those with no realistic hope of ever escaping poverty to enjoy rewards such as a decent house, a challenging job or a fun vacation, or those who have regular experience of losing people or assets they value, perhaps focusing on cheap, immediate pleasures such as cigarettes or fried food is an entirely rational response.
But psychologists including Greg Miller think there is another factor too. Research suggests that stress in early life doesn’t just make people more vigilant for threat. It also affects reward circuits in the brain that regulate our appetites for everything from food to drugs, sex and money.
In addition to the amygdala, the prefrontal cortex helps to regulate other brain regions including the nucleus accumbens, which is part of an area called the ventral striatum. The nucleus accumbens makes us want things, and it plays an important role in addiction. Messages from the prefrontal cortex to the nucleus accumbens temper our desire, reminding us of the consequences of our actions, and helping us to forgo immediate gratification for greater rewards in the future.
There’s preliminary research suggesting early stress affects how these circuits too are wired as the brain matures, weakening this top-down control throughout people’s lives. Those from low socioeconomic backgrounds are more likely to prefer smaller immediate rewards over larger postponed ones, regardless of their current life circumstances.49 A 2011 brain imaging study asked 76 adults to play a game in which they could win or lose money.50 When they learned of their winnings, those from poorer backgrounds had reduced prefrontal cortex activity, and weaker connections between the prefrontal cortex and the ventral striatum.
Someone with a brain wired in this way is likely to prioritize immediate pleasure over future consequences. They’ll be impulsive, and at risk for unhealthy behaviors such as eating high-fat foods, addiction and risky sex. Like being hypersensitive to threat, this makes sense from an evolutionary point of view—if you’re in an environment where resources are scarce and there are dangers everywhere, it’s a good strategy to gorge on calorie-filled food when you find it, for example, or to breed young. But in the modern world, these behaviors make it harder for people to escape poverty, and at the same time, ruin their health.
In several different ways, then, stress can rewire the brain in a way that puts people struggling with adverse environments at an even greater disadvantage—and sets them up for a lifetime of chronic illness. This cruel legacy helps to explain why people who are exposed to stress, like Monica, make the choices they do, and why they still suffer health effects even if their circumstances improve. But it also raises a question. Can these changes in the brain be prevented, or even reversed?
It’s seven in the morning and I’m walking along the beach in Santa Monica, California. The low sun glints off the waves and the clouds are still golden from the dawn. Curlews and sandpipers cluster on the damp sand, while in the distance, white villas of wealthy Los Angeles residents dot the Hollywood Hills.1
For half a mile or so, the beach is close to deserted. Then, just north of lifeguard station 27, I find what I’m looking for. In a neat line, a few yards back from the water’s edge, a handful of people sit cross-legged on towels. They’re members of a local Buddhist group, about to begin an hour-long silent meditation. I take my place at the end of the row, facing out to sea.
For centuries, followers of Eastern religious traditions have meditated in search of spiritual enlightenment. The practice came to the West in the 1960s as part of hippie counterculture, endorsed by celebrities and bands such as the Beatles and the Doors. Since then it has grown in popularity as people seek peace and meaning amid the material concerns of modern life; it now seems no more notable to see meditators on a California beach than in a temple in Tibet.
I’m not here on a spiritual quest, however. I’m interested in scientific claims that meditating can improve physical and mental health by reducing stress. Of all areas of mind–body medicine, meditation, with its close links to religion and spirituality—not to mention mind-expanding drugs—has had a stormy relationship with science. Various studies since the 1970s have suggested that meditating monks can achieve a range of striking physical effects, from voluntarily reducing blood pressure to flooding their brains with highly synchronized electrical waves.
Some researchers, with close links to religious organizations, have been accused of finding what they want to see. And although monks who have spent much of their lives in remote retreats are undoubtedly capable of some stunning feats, it’s not clear how relevant that is for the rest of us. In the last decade or so, however, a new generation of brain imaging studies and clinical trials has put meditation firmly on the scientific map. They’re showing that although watching our thoughts might seem ephemeral, it can have hard physical effects on our brains and bodies.
But first, it’s time to give this mysterious practice a
try. There are hundreds of ways to meditate: compassion meditation involves extending feelings of love and kindness to fellow living beings (we’ll learn more about this in chapter ten); transcendental meditation has people focus on a repetitive mantra. Mindfulness, meanwhile, involves being aware of your own thoughts and surroundings. This is one of the most popular—and most studied—practices, so this morning I try a form of mindfulness meditation called open monitoring. Sit upright and still, and notice any thoughts that arise. Don’t judge or react to them, just let them go.
I settle on my towel and start to contemplate the sparkling water. The view stretches out over thousands of miles of Pacific Ocean, and it is breathtakingly beautiful. Facing this vast expanse without thoughts and daydreams to fill my attention is slightly unnerving, however. My head is usually a tangle of ideas and words; spoken, written, heard, imagined, remembered. I’m not sure they will be so easy to banish.
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I’M NOT alone in filling my head with abstract thoughts, says Mark Williams, emeritus professor of clinical psychology at the University of Oxford, U.K. He’s an expert in the psychological effects of meditation, and co-author of a 2011 book called Mindfulness that explains how training the mind to be more aware can reduce stress and anxiety in daily life. It became a surprise bestseller, with testimonials from celebrities such as Ruby Wax and Goldie Hawn.
“Most of us are preoccupied moment by moment, we’re not actually aware of where we are or what we’re doing,” he tells me. “We’re usually planning the future, or re-running something that has happened.”2 When you’re doing the dishes, for example, you might be thinking about the cup of tea you’re going to have. When you’re drinking the tea, you’re planning your trip to the supermarket. When you’re driving to the supermarket, you’re thinking about what you’re going to buy.