As modern-day stress ratchets up to what feels like unbearable levels, researchers are striving to learn more about the precise mechanisms through which it affects our body and mind. The hope is that by unlocking more about how stress works physiologically, we can find ways to prevent it from permanently harming people.
Over the last five decades, scientists have established beyond doubt that persistent stress really can poison our overall health. In addition to increasing the risk of cardiovascular disease, stress plays a role in obesity and diabetes and can weaken the immune system, leaving us more vulnerable to infectious diseases. You can recover swiftly from an episode of acute stress—for example, the alarm one might feel when caught unprepared for a presentation. Chronic stress, on the other hand, is more toxic as it is an unrelenting circumstance that offers little chance for a return to normalcy. Financial strain, having a bully for a boss, and social isolation are all examples.
Inside the Computer Assisted Rehabilitation Environment Laboratory at Walter Reed National Military Medical Center in Bethesda, Maryland, Army veteran Wayne Christian walks toward an emotionally triggering photo of himself. Studies indicate that by helping patients confront traumatic memories and process the negative feelings around them, this advanced treatment reduces the symptoms of severe post-traumatic stress disorder.
Today chronic stress seems to be increasing worldwide, as people grapple with rapid socioeconomic and environmental change. A 2023 national survey by the American Psychological Association found that stress has taken a serious toll since the start of the pandemic, with the incidence of chronic illnesses and mental health problems going up significantly, especially among those ages 35 to 44.
(Do you have chronic stress? Look for these signs.)
So far, one of the major realizations among scientists is that stress harms all of us in different and powerful ways. But is there any way to avoid it—or at least recover more quickly? Some promising avenues of research offer hope for the future.
High school junior Zainab Khorakiwala undergoes a functional MRI as part of a study by Harvard’s Stress and Development Lab examining how everyday stress affects teens’ brain development.
Preventing chronic stress from harming you in the first place
Groundbreaking studies in orphans showed how stress in early life can leave an indelible mark on the brain.
“Chronic stress in early life has more serious and lasting effects, because that’s when a lot of connections are being laid down in the brain,” says Aniko Korosi, a researcher at the University of Amsterdam who has been conducting experiments on mice to elucidate that link between early-life stress and brain development.
Korosi may have found a surprising link between stress and the resulting nutrient composition in the brain. She and her colleagues noticed that mouse pups that had been exposed to stress in the first week of their lives—having been moved from their mother’s care to a cage—had lower levels of certain fatty acids and amino acids in their brains compared with pups being raised in a stress-free environment.
She wondered if it was possible to normalize a stressed pup’s development by feeding it a diet rich in the specific nutrients its brain would be lacking. To find out, the researchers first fed a supplemented diet to the mothers so it would pass through their milk, then continued to provide it in the pups’ feed for two weeks after they were weaned. A few months later, the researchers tested the now adult mice in learning and memory. Unlike stressed mice that had never received an enriched diet, these mice did not display cognitive impairments.
(How wild animals cope with stress—from overeating to sleepless nights.)
“I was surprised that changing the nutrition could have such a powerful effect, because it’s such an easy intervention,” Korosi says.
If further studies provide more evidence of the nutritional pathway, she says, there would be a strong basis for supplementing the diets of infants born to mothers living in stressful conditions.
Developing an early warning system for stress
Katie McLaughlin, a psychologist at the University of Oregon, is investigating how mental health problems arise in adolescents as they’re going through a particularly vulnerable time in their lives, transitioning to adulthood.
She and her colleagues are still collecting data, but a smaller, precursor study tracking 30 teenagers offers clues about what the researchers might learn—and how it might help them identify stress before it goes too far.
Monochromatic brain scan of a young girl highlights two sections in bright orange where emotional stimuli indicates signs of child maltreatment. Research into individuals who suffered abuse as children shows that their brains react strongly to emotional stimuli.
Tyler C. Hein and Christopher S. Monk, University of Michigan
In that study, McLaughlin found that the extent of stress experienced by a subject in the month before their lab visit changed how their brain responded to emotionally impactful information such as when they were shown a picture of a threatening face. The brain’s prefrontal cortex, which helps regulate emotions, showed less activation when the subject had experienced higher levels of stress.
McLaughlin is optimistic that data from the ongoing study will help pinpoint changes in behavior as well as brain activity that predict the emergence of mental health problems like anxiety and depression. This could enable the development of targeted interventions delivered to teenagers at just the right time, she says. If the identified marker of stress were a sudden decrease in sleep duration or a sharp decline in social interactions, for example, it would be possible to push the intervention out to the individual on their smartphone.
“Like, here’s a reminder about good sleep hygiene, or this might be a good time to check in with your counselor at school about what’s been going on in your life,” McLaughlin explains.
(‘Hysterical strength’? Fight or flight? This is how your body reacts to extreme stress.)
Learn more about stress and how to manage it
Preventing inflammation caused by chronic stress
Gaining a deeper understanding of how stress affects the immune system may also help find a way to reverse those effects.
In the 1980s, psychologist Janice Kiecolt-Glaser and her virologist husband, Ronald Glaser, began exploring the physiological impact of stress on two notably stressed segments of society: medical students and older caregivers. The researchers found the students’ immune systems were less robust when they were taking exams than during non-exam times—and that stress altered the body’s response to vaccines.
Before her husband, Tommy, who suffers from Alzheimer’s disease, moved to an assisted-living facility this year, caring for him took nearly all Ellen Ebe’s time and energy. She participated in an Ohio State University study on how such caregiving affects the body’s ability to fight disease, as well as the risk of depression and anxiety.
Researchers then administered the flu and pneumonia vaccines to individuals responsible for a spouse with dementia. Unlike medical students taking exams, who were likely stressed only in the short term, these people were experiencing unrelenting stress. When tested at set periods after inoculation, they had fewer antibodies compared with a control group—they couldn’t maintain their protective response. “That gave us good evidence that the changes brought on by stress were biologically meaningful,” says Kiecolt-Glaser, now an emeritus professor at the Ohio State University.
Around the same time, researchers led by Sheldon Cohen, now emeritus professor of psychology at Carnegie Mellon University, delivered cold-causing viruses into the nostrils of about 400 adult volunteers in the U.K. “The more stress they reported prior to our exposing them to a virus, the higher the risk was for them to develop a cold,” says Cohen. The duration and type of stress mattered: Chronic economic or interpersonal stress were what really put people at high risk—and the longer it went on, the greater the susceptibility to falling sick.
Detention center officers participate in an active shooter training session at a former middle school in Texas. Law enforcement officials have a higher risk of cardiovascular disease compared with the general population. Even situations that officers know are drills have been shown to increase physiological stress markers.
Cohen and his colleagues also learned that when exposed to viruses, chronically stressed people tended to produce an excess of cytokines—proteins that serve as messengers of the immune system, traveling to sites of infection and injury and activating inflammation and other cellular processes to protect the body. Too many cytokines cause an excess of inflammation.
Researchers still don’t know enough about how stress alters the immune system’s ability to regulate cytokines to devise an intervention to reduce the inflammation, but in one way, these findings signal some hope: There are clear targets for more work to be done.
Understanding stress on a cellular level
The future of understanding and combating stress may lie in our DNA.
In 2023, Ursula Beattie, then a doctoral student at Tufts University, and her colleagues found possible evidence that stress can overwhelm DNA’s repair mechanisms. In their study, researchers repeatedly tapped on sparrow cages with pens, played the radio loudly, and other actions designed to cause distress but no physical harm. Blood and tissue samples from the sparrows after three weeks of this unpleasant treatment revealed damage to the DNA. “It’s like if you had two pieces of string coiled up, just like DNA, and you took a pair of scissors and cut them,” Beattie says.
While these kinds of double-strand breaks in DNA occur all the time in sparrows and other species, including humans, the damage is typically reversed through self-repair mechanisms. In a chronic-stress setting, “those repair mechanisms get overwhelmed, which is how we see a buildup of DNA damage,” Beattie explains. The damage in the birds appears to be the most severe in cells of the liver, she adds, suggesting that for humans, too, the extent and type of damage inflicted by stress might be different for different tissues of the body.
Separately, Kiecolt-Glaser and psychologist Lisa Christian at OSU are conducting a longitudinal study to determine whether chronic stress ages you more quickly. If results support a smaller, earlier study, it appears that chronically stressed caregivers not only are more likely to get sick and heal more slowly but they also show signs of accelerated aging.
We’re still learning how deep stress goes into our bodies. But these exploratory findings mean we’re getting closer to solving the puzzle that is stress, which promises a future where we can better meet the ongoing demand for change.
(20 stress-relief gifts for the frazzled friend in your life.)
Carline Raphael (at left), a public health worker in New York City, visits with new mother Marisela Bravo Berrera and her two-month-old daughter, Angel, to give advice on breastfeeding and good sleep habits for newborns. Research shows chronic stress alters the nutritional components of breast milk, so stress management for mothers of infants is key to the babies’ healthy development.
Yudhijit Bhattacharjee has written more than a dozen National Geographic features, many of which delve into the science of human experience, including our cover story on stress. A contributing writer at the New York Times Magazine and author of The Spy Who Couldn’t Spell, he manages stress by singing.
Brian Finke has photographed multiple features for National Geographic, including the science of taste and The Carnivore’s Dilemma. His work has been published in several books and featured in museum collections around the world. He manages stress by cycling around New York City.
A version of this story appears in the June 2024 issue of National Geographic magazine.
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