Maybe a walk in the woods surrounded by birdsong, the silence of morning meditation or evening prayer calms your mind. Maybe the rhythm of knitting or the earthy smell of gardening clears your head.
Science now supports what we intuitively know: spending time in nature or pursuing calming habits and hobbies has a positive impact on our mental and physical health. These activities rejuvenate us, right down to the living components of our bodies: our cells.
A research team from the University of California, San Francisco, led by Dr. Alexandra Crosswell and Dr. Elisa Epel, combined their research with that of others in a variety of fields and found that experiences such as painting or practicing yoga can lead to changes in the nervous system and, ultimately, to changes in cells. Our bodies and minds need certain conditions to make these changes happen. But once they are met, they say, the results are as follows: Deep Rest.
This truly restorative state has never been described before and provides benefits that cannot be achieved through routine rest and relaxation. In proposing the concept, the team highlights the regenerative biological processes that protect us as we age.
“Deep rest is something our bodies need and deserve,” said Epel, professor of psychiatry and vice chair of psychology. “Rest improves our chances of living a long, healthy life.”
How chronic stress harms us at the cellular level
To understand the benefits of deep rest, we must confront its opposite: stress. According to a survey by the American Psychological Association, Americans experience this stomach-churning condition all the time: Nearly half of adults surveyed in a 2023 survey at least somewhat agreed that “stress makes me dread going to work.” [or] “School is getting harder.”
Although stress can hinder our functioning, it originates from physiological mechanisms that help us deal with challenges, like fleeing a pack of wolves or facing the consequences of making a major mistake at work. Similar to the fear of being eaten, the threat of losing the respect of a colleague puts the body on alert and triggers a series of responses.
Your nervous system cedes control of unconscious processes like breathing and digestion to your crisis response coordinator, the sympathetic nervous system. This shift sets off a series of energy-hungry changes that prepare your body and mind for action: Your heart rate increases. Blood flow to skeletal muscles increases, causing muscles to tense up. There’s a surge in hormone production, including energy-giving chemical messengers like cortisol. Attention increases.
These and other changes combine to help prepare you for fight or flight, even if you’re just anxiously waiting for a response to an apologetic email while imagining dire scenarios.
Some level of stress is inevitable in life, Crosswell points out. “After years of studying stress, it’s become clear to me that we need to stop trying to eliminate stress,” she says. “Stressful events are often outside of our control, and our body’s response to them is natural and beneficial.”
But too much stress can be harmful. She and her colleagues argue that many Americans spend most of their waking hours in a state of moderate stress, driven by feelings of anxiety about the future and a lack of control. While it won’t come as a surprise to many of us, the idea that we’re continually stressed, which the team explores, marks a new direction in scientific thinking, where a state of relaxation has traditionally been considered the human default state.
Ideally, a stress-inducing crisis will have a swift, clean end. Workplace apologies might be accepted, and mistakes quickly forgotten. But the problems of modern life often don’t reach a complete conclusion right away. Your boss might repeatedly reject requests to work remotely. You and a loved one might argue frequently. You might struggle financially for years. In these situations, stress may subside to more moderate levels, but it never stops.
Though less taxing, residual stress still drains you. It takes extra energy to keep your heart rate high or secrete more cortisol than usual. This energy comes in the form of a molecule called ATP (adenosine triphosphate). Cellular organelles called mitochondria use oxygen from the air we breathe to harvest energy from fats, proteins, and glucose from the foods we eat to produce ATP.
“Mitochondria are the life force that gives cells life and ultimately our consciousness and emotions,” says Martin Picard, PhD, director of the Mitochondrial Psychobiology Group at Columbia University and one of Epel and Croswell’s collaborators.
“Everything we experience is driven by the flow of energy within our cells,” he says, “and that flow happens in the mitochondria.”
Each cell contains hundreds of mitochondria, but for reasons that are unclear, these organelles can only produce a limited amount of ATP. So when the body is on alert, cells divert their limited ATP supply to perform emergency functions required for the stress response, like contracting the heart or synthesizing hormones, which takes away energy from more mundane but necessary tasks.
Additionally, studies have linked diseases like diabetes, heart disease, and neurodegenerative disorders to poor mitochondrial health. Picard suspects that psychological stress may have a similar effect, with chronic stress damaging mitochondria and reducing productivity.
Several previous studies into the causes of chronic stress in mothers raising children on the autism spectrum, as well as Epel’s own research, support this idea. Biological PsychiatryPicard and his colleagues found that the mitochondria in the mothers’ white blood cells were less able to convert energy into ATP. Another potential consequence of damaged mitochondria is that cells may face increased production of reactive oxygen species (ROS), a potentially toxic by-product of ATP production. If not neutralized, ROS can harm cells.
Chronic stress also affects genetic material. At the ends of chromosomes, repeated sections of DNA form telomeres. Telomere “caps” protect the integrity of these packets of genetic code as long as possible with the help of proteins.
Each time a cell copies and replicates its genetic material, telomeres lose a little DNA and shorten. Research that Epel began 20 years ago with UCSF colleagues Nobel laureates Dr. Elizabeth Blackburn and Dr. Jue Lin has found that chronic psychological stress shortens telomeres even further. This shortening is the result of exposure to ROS, the release of hormones like cortisol, and inflammation. Molecular studies of cells have demonstrated this connection. By mimicking chronic exposure to the stress hormone cortisol, Picard has shown that cells respond by increasing their metabolism, shortening telomeres and hastening cell death.
