Part of the challenge going forward will be to match the treatment to the individual. In the past several years, researchers have realized just how much the impacts of stress vary depending on someone’s biology, past exposures and present circumstances.

For one thing, men and women tend to differ in their responses6. Men show greater cortisol responses to stressors related to performance, for example, such as public speaking, whereas women might react more strongly to inter-personal stressors7. Some studies find that people whose microbiome is out of balance, because of antibiotics or previous stressors, can experience an exaggerated stress response.

There’s also a body of research on how children who experience abuse or chronic neglect can be predisposed to a maladaptive stress response later in life. “An early-life traumatic experience can lead you to believe the world is unpredictable and unsafe place,” says Slavich.

In the future, Slavich says, having a comprehensive profile of a person could guide a health-care team to the best combination of interventions for them.

He and his team are testing such an approach by pairing personal stress profiling with tailored treatments. The team matched more than 400 participants in California to one of five 12-week interventions on the basis of how individuals reported being affected by stress8. The treatment programmes focused on improving either sleep, eating habits, physical activity, cognitive responses or social relationships through weekly pre-recorded videos, digital modules, a coaching session and an assessment. The researchers are now analysing data collected on a variety of psychological, emotional, biological and behavioural outcomes — from sleep to the diversity of bacteria in the gut.

Rewiring resilience

Other treatment options could emerge from new ideas about how stress contributes to disease in the long-term. One theory centres on mitochondria, the powerhouses of cells. It suggests that psychological stress drives disease and accelerates ageing, in part, by using up too much cellular energy9, creating oxidative stress that can damage cells and tissues. And because mitochondria are extremely sensitive to inflammation and oxidative stress, the effects can amplify in a harmful feedback loop.

Martin Picard, a psychobiologist at Columbia University in New York City and one of the proponents of the link between mitochondria and ageing, says it could explain many of the ways in which stress affects the body — including greying hairs. During a bout of grant-writing stress in 2017, five of his own auburn hairs turned grey, reverting back after a holiday.

“Hair colour is one of the most futile, dispensable features of our bodies,” says Picard. “If the body runs out of energy, it makes sense that it would ‘de-prioritize’ making pigment for hairs.”

Picard suspects that interventions, including meditation and exercise, could help to boost the quality and function of mitochondria. And if the theory is correct, it might even support the use of psychedelic therapy for people with post-traumatic stress and other stress disorders, he says. There are early hints that psilocybin, LSD and other hallucinogens act on a cell-surface receptor10 that seems to be involved in increasing the production of healthy mitochondria.

Targeting the microbiome is another emerging avenue. Research over the past couple of decades points to bidirectional communication between the brain and gut, with stress disrupting the microbiome and a disrupted microbiome exacerbating the stress response.

John Cryan, a neuroscientist at University College Cork in Ireland, and his team have shown that supplementing the diet with specific strains of gut bacteria that are naturally present — yet often depleted — dampened the stress response in both laboratory animals and humans. The same effects didn’t show up in mice with a severed vagus nerve11, pointing to that nerve’s central role in gut–brain communication, says Cryan. Research by Mendes and others is also showing that direct stimulation of the vagus nerve might modulate the stress response.

Finding solutions doesn’t just benefit the individual. Through behaviours driven by stress and inflammation — including impaired decision-making — one person’s stress can make others stressed, says Julia Concetta Arciero, a mathematician at the University of Indiana in Indianapolis.

Last year, Arciero co-authored a paper that used mathematical models to study the links between individual stressors and large-scale societal dysfunction over time12. “The decisions people make, the actions they take, they’re all very interactive without us realizing it,” says Arciero.

Almeida, who wrote an editorial13 accompanying the paper, says the effects of stress go beyond individuals and beyond health problems. “If we’re not making good decisions, or we can’t help each other because we’re all stressed, that could be a daunting future.”

But eliminating stress entirely is not the answer, says Elissa Epel, a behavioural scientist at the University of California, San Francisco, and a pioneer in research on the mitochondria–ageing theory. Even though stress often causes damage at the cellular level, research by her team and others shows that brief bouts of well-regulated stress can bolster mental and physical health and strengthen resilience to future stress14.

Stress can even fuel action and ignite a positive feedback loop that might mitigate the burden of stress across society, says Almeida. Whether the stress is driven by moral outrage at injustice or by climate change, “it’s motivation for activism”, he says. “That typically doesn’t happen if you don’t feel threatened or challenged.”