Why Doctors Are Prescribing Nature Walks

In early April 2022, about two dozen children and their families gathered beneath the redwoods in a regional park near Oakland, Calif. They sat with a physician, Dr. Nooshin Razani, beneath the branches of the ancient giants, breathing the fresh air and discussing the phenomenon of fairy rings—when a mama tree is cut down, the baby trees grow up in a circle surrounding the stump of the parent tree.

These families are taking part in a program Razani runs at the University of California San Francisco Benioff Children’s Hospital Oakland. (Marc and Lynne Benioff, who are philanthropic supporters of UCSF Benioff Children’s Hospital, are co-chairs and co-owners of TIME.) The program, called the Center for Nature and Health, takes pediatric patients who are dealing with conditions like anxiety, autism, obesity, or developmental issues—and who live in areas without much nature nearby—into local parks on excursions with park staff each month.

The program is part of a growing trend of so-called “park prescriptions,” which have increased in popularity over the last decade along with research into the health effects of spending time in nature. In these programs, physicians strongly encourage patients young and old to spend more time outside to improve their mental and physical health.

“It’s pretty clear that it’s good for you,” says Razani. Research suggests living near green space and recreating in nature can improve mental health and reduce the risks of certain physical health conditions, like heart disease. Scientists are still trying to figure out why, but the leading theory is that spending time in nature reduces stress, a state that’s tied to many health problems.

Of course, no doctor is advising patients to spend a day at the park instead of prescribing needed anti-anxiety medications, for instance. Nature is not a cure for health issues—and park prescriptions aren’t meant to be used instead of prescriptions for medications. But people can harness real health benefits from their nearest patch of nature.

A history of park prescriptions

Nature prescriptions come in many forms, but these types of programs all provide a way for doctors and other healthcare professionals to encourage their patients to spend time in nature. In Walk with a Doc, started by a cardiologist in 2005, health care providers lead strolls in their community; the walks have expanded to more than 500 places around the world.

ParkRx, which became one of the first park-prescription programs in the U.S. when it launched in 2013, provides health care practitioners with guides, toolkits, and case studies to help coax their patients outdoors. PaRx in Canada, which officially launched in 2020, was inspired by these programs. The PaRx website provides copious evidence for the health effects of nature and fact sheets for physicians. PaRx also created a virtual nature prescription that doctors can include in a patient’s electronic health record. Already, more than 5,000 healthcare professionals use the program.

Nature prescribing has traction overseas as well. Doctors in Scotland started writing nature prescriptions for patients in 2017 in collaboration with the Royal Society for the Protection of Birds Scotland and the National Health Service (NHS). During the pandemic, the NHS also created a referral network to connect patients with nature-based activities, like walking and community gardening.

How nature improves health

Everyone’s health could benefit from a closer connection to nature. But not everybody has equal access. Wealthier neighborhoods tend to have more green space than poorer neighborhoods. That’s partly why Razani’s program focuses on children who do not have adequate green space close to home. Often, these are the populations who need the healing benefits of nature the most. “The end condition the clinician is seeing may vary, from obesity and anxiety,” she says, but two important upstream reasons for these conditions are “stress and lack of access to outdoor space.”

When the body is stressed, it undergoes physiological changes, says Mat White, a health and environmental psychologist at the University of Vienna in Austria. Stress stimulates the release of the stress hormone cortisol, which in turn raises your blood pressure and heart rate. Chronically elevated levels of stress are connected to anxiety and depression, he notes. Stress has also been connected to heart disease, obesity, and other negative health outcomes.

Scientists think that having positive experiences in nature can help alleviate stress and reduce cognitive fatigue, thereby improving health. “The major theories in the field currently coalesce around the idea of stress reduction,” White says.

These theories are based on research that started gaining traction around 2010, experts in the field say. Many studies have found correlations between spending time in nature and improved mental or physical health. “We know there’s a robust relationship between mental health and nature exposure,” says Matthew Browning, founding director of the Virtual Reality and Nature Lab at Clemson University who studies the link between the natural world and human health. There’s also a relationship between long-term exposure to nature and reduced risk of cardiovascular disease and death from any cause, he says. One major early study in the field, published in 2008 in the Lancet, found that people in England living in greener areas had lower rates of death from circulatory diseases and from any cause. “Physical environments which promote good health may be important in the fight to reduce socioeconomic health inequalities,” the authors wrote in the study.

People who live in greener areas also tend to have lower health care costs, says Browning. In a study published in the May 2022 issue of the journal Environment International, Browning and his colleagues examined the total health-care costs of 5 million people in Northern California over a decade and compared those costs with the amount of green space or trees around each person’s home, determined through satellite data. Living closer to green areas was correlated with lower health care costs, and the link persisted regardless of other factors that can affect health outcomes, like income, education, occupation, and housing conditions.

When it comes to how nature exposure helps our stressed-out brains, researchers have two main theories, says Gregory Bratman, director of the environment and well-being lab at the University of Washington. The first, known in scientific circles as the Stress Reduction Theory, is that exposure to many forms of nature engages the parasympathetic nervous system, which is responsible for rest and digestion and encourages stress recovery. (It’s nicknamed the “rest and digest” system.) The other, the Attention Restoration Theory, suggests that nature engages people’s “soft fascination,” says Bratman. This gives our directed attention, which we use to focus, time to replenish, he says.

Much of the research has focused just on the visual aspects of nature—seeing the green of trees or grass, or the blue of a river or ocean. But “nature experiences are multi-sensory,” notes Bratman. Practitioners of shinrin-yoku (or “forest bathing”) in Japan theorize that the scent and experience of breathing in the compounds that trees exude into the air could impact immune function, says Bratman. Sound is another key sense that may indicate safety or danger, allowing relaxation or exacerbating stress—and soothing nature sounds fit firmly in the first camp, says Rachel Buxton, a conservation scientist at Carleton University in Canada, who studies soundscapes, seabird ecology, and ecological restoration.

Future research

Scientists still don’t know everything about how nature affects health. Many of the studies that find a relationship between the two just look at trends in the general population—not within specific groups, like people with anxiety or depression, says White. Establishing the direct effects of nature on certain conditions would involve ethically complex experiments on small groups of patients, he notes. Because of these complications, scientists don’t have much high-quality evidence as to how nature could affect those people who, theoretically, are in most need of a park prescription.

It’s also possible that pressuring someone to spend more time in nature might reduce some of the benefits of the visit, says White. In a study published in 2020, White and his colleagues found that feeling social pressure to visit nature was associated with a higher likelihood to get outside, but also with less personal motivation, less happiness during the visit, and higher anxiety. As soon as you tell someone to do something, “there’s a chance it undermines people’s intrinsic enjoyment,” says White.

Many important questions about how to maximize a nature prescription remain unanswered. “We don’t really know how much time people need to spend in nature, [or] what types of nature,” says Browning. The quality of nature someone is exposed to is also likely important, but researchers are not quite sure what that means. Is a manicured park with turf grass and a ballfield enough, or do people benefit more when they go out in the woods—somewhere rich in biodiversity? What’s more, the type of nature someone finds relaxing could be highly individual, based perhaps on their familiarity with a particular landscape, says Browning.

Scientists are working to fill in these knowledge gaps. Razani, for example, recently received a $1.2 million grant to study the effects of her nature intervention on anxiety in children. And the scientific literature is constantly growing in this area, says Ulrika Stigsdotter, a professor of landscape architecture and planning at the University of Copenhagen in Denmark, who focuses on evidence-based health design for outdoor spaces.

Some of that research revolves around how outdoor spaces can be better designed specifically for nature therapy, Stigsdotter notes. If researchers hope to use nature-based treatments to improve the health of specific patient groups, like those with anxiety or depression, the setting really matters. The design of a garden or landscape needs to fit who will be using it, she says: Someone with cancer may respond to certain garden designs differently than someone struggling with depression or someone else who recently moved to a retirement facility. “The treatment program depends on the context,” she says.

In the general population, it’s also important not to overstate the effects of nature, says White. “These effects of green and blue space are small” for most people, says White, particularly compared to other factors that affect our health like relationships, job satisfaction, and financial stability. “They’re marginal effects, but they apply to millions of people. So the overall public health benefit is huge, but small for any given individual.”

Harnessing these health impacts across entire populations will necessarily mean expanding access. A prescription to get outside can’t address the issues surrounding access to green space. It can’t expand green space in neighborhoods that lack them, or guarantee that vulnerable people feel comfortable going to these green spaces, or combat all the stress and illness people face.

“If we had healthy ecosystems [available to] all income levels, we wouldn’t need to take excursions into nature,” says Razani.

Still, Razani has seen the power of her program in action. She’s seen a little boy with developmental issues come alive learning about trees, impressing the park naturalist with his deep knowledge. She’s watched another child with autism and anxiety became calm, engaged, and confident while exploring a regional park. The adults involved in the program transform too, she says. One mother, a survivor of domestic abuse, brought her daughters and eventually started leading nature outings herself for other survivors.

The more researchers learn about the stress-reducing powers of nature, “what public health people have always been saying—that health starts outside the clinic—is just becoming more and more apparent,” says Razani.