Earlier this month, Dr. Robert Zarr, a pediatrician in Washington, DC, met with a young patient who’d been spending most of his time in front of screens. The 10-year-old boy had settled into a sedentary lifestyle when school went online during the pandemic. He could go days without leaving his house and, Zarr determined, he really needed to lose some weight. 

During the checkup, Zarr discovered his patient absolutely loved riding his bike. So, he wrote him a prescription to cycle to and around a park near his house for at least 45 minutes, three times a week.

While we might associate prescriptions with pills, a growing number of healthcare providers, including primary care physicians, psychiatric nurse practitioners and cardiologists, are pulling out their Rx pads to scribble down regimens for outdoor exercise, not medication. Nature prescriptions are part of a larger movement called social prescribing.

The idea is to treat mental and physical chronic conditions such as anxiety, depression and obesity through simple, accessible activities, like a walk in the park or a bike ride through the woods. Zarr always includes four things in his prescriptions: the recommended activity, place, cadence and time frame. Sometimes social interactions are recommended too; nature prescriptions may differ slightly based on who’s writing them. 

Additionally, large nature prescription programs have emerged to impose structure on the movement. Prescription Trails, the first such program in the US, was founded in Albuquerque in 2006 to encourage patients with chronic illnesses to get outside and move. In 2017, Zarr founded his own prescription program called Park Rx America. 

Although each program is unique, most offer maps of outdoor spaces in a given geographic area, digital platforms for doctors and patients to administer and fill prescriptions, and a way for patients to sign up for structured outdoor activities. In the US, there are now at least 100 nature-prescription programs in 34 states. But, currently, there aren’t any standardized protocols for prescribing nature or shared database where different programs log prescriptions. So information on the practice is still fairly limited.

Why “prescribe” nature in the first place? Because, well, the great outdoors are a boon to your health and well-being, according to just about every measure.

For years, the Japanese have cultivated the art and benefits of Shinrin-yoku, or forest bathing. And in recent years, research has shown that outdoor time can lead to lower stress levels and increased amounts of physical activity — two health outcomes important in combatting common chronic illnesses.

Nature’s positive mental impact is also extremely well-supported. One 2015 study found that nature walks could lower someone’s risk of engaging in harmful behaviors like rumination, as well as developing mental-health disorders like depression. Another found that merely listening to crickets chirping, without even being in nature, could enhance focus on complex tasks. 

Studies have similarly demonstrated nature’s physiological effects. A 2019 study linked self-reported “good health” with at least 120 minutes of green-space time per week; another found that children’s BMIs decreased when they spent time outdoors.

It’s not as though doctors didn’t recommend exercise to patients before nature prescriptions came along. Still, Zarr and other proponents of the practice believe it has advantages over a doctor merely telling someone to go for a jog. For one thing, patients feel more accountable for their lifestyle choices when they get instructions on exactly how to get outside and sweat, versus general directives to be healthier. Zarr hopes that his and similar programs can help Americans control the spread of obesity and diabetes.

The mental health community has embraced nature prescribing too. “From an evolutionary perspective, our brains are really adapted to being in nature,” says Amy Lajiness, a therapist based in La Jolla, California. “That is our home.” 

While nature prescriptions are generally growing in popularity, there isn’t much research on the best way to design the process for providers or health systems, in order to account for practical constraints like time. With doctors’ appointments averaging about 13 to 16 minutes long, can clinicians feasibly develop detailed nature prescription during a visit? Experts need to figure that out.

Importantly, we also don’t yet know how well these prescriptions work for the conditions they’re supposed to treat. One recent review looked at 11 different studies, plus other types of papers, charting the effectiveness of nature prescriptions in preventing everything from stress to obesity. The review concluded that research findings were “mixed,” and that the literature is still “too sparse” to offer persuasive evidence of efficacy.

We likely won’t have more data for a few years. Dr. Zarr, for instance, is currently in the second year of a five-year study designed to see how well park prescriptions can treat obesity in teenagers.

Nevertheless, COVID-19 lockdowns illuminated the power of nature in a way we never could have imagined, says Diana Allen, chief of the National Park Service’s Healthy Parks Healthy People programming. In a study of nine countries under lockdown, researchers found contact with nature reduced the likelihood of participants developing depression and anxiety. This was true even when participants stared through a window at “blue-green space,” meaning any area with greenery or water, or both. 

Fittingly, the National Park Service has its own prescription program, ParkRx, and this year, NPS is celebrating a 100-year-partnership with the United States Public Health Service through “The Power of Parks for Health,” a campaign about the intersection of nature and health. “This is a growing movement,” Allen says. “People are understanding the importance of getting outdoors when we were forced to be indoors.”

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