Is Nature Your Brain’s Miracle Medicine?

When you go to the desert with David Strayer, don’t be surprised if he sticks electrodes to your head. A cognitive psychologist at the University of Utah who studies the mind’s ability to think clearly, Strayer understands the relentless distractions that pummel our modern brains. But as an avid backpacker, he thinks he knows the antidote.

On the third day of a camping trip in the canyons near Bluff, Utah, Strayer, sporting a rumpled T-shirt and a slight sunburn, is mixing an enormous iron pot of chicken enchilada pie while explaining the “three-day effect” to 22 psychology students. Our brains, he says, aren’t tireless three-pound machines; they’re easily fatigued by our fast-paced, increasingly digital lives. But when we slow down, stop the busywork, and seek out natural surroundings, we not only feel restored but also improve our mental performance. Strayer has demonstrated as much with a group of Outward Bound participants, who scored 50 percent higher on creative problem-solving tasks after three days of wilderness backpacking. (Is forest bathing worth a shot?)

“If you can have the experience of being in the moment for two or three days,” Strayer says as the early evening sun saturates the red canyon walls, “it seems to produce a difference in qualitative thinking.”

How does nature help our brain?

Strayer’s hypothesis is that being in nature allows the prefrontal cortex, the brain’s command center, to rest and recover, like an overused muscle. If he’s right, when he hooks his research subjects—in this case, his students and me—to a portable EEG device, our brain waves will show calmer “midline frontal theta waves,” a measure of conceptual thinking and sustained attention, compared with the same waves in volunteers hanging out in a Salt Lake City parking lot.

Strayer has his students tuck my head into a sort of bathing cap with 12 electrodes embedded in it. They adhere another six electrodes to my face. Wires sprouting from them will send my brain’s electrical signals to a recorder for analysis. Feeling like a beached sea urchin, I walk carefully to a grassy bank along the San Juan River, where I’m supposed to think of nothing in particular, just watch the wide, sparkling water flow by. I haven’t looked at a computer or cell phone in days, and it’s easy to forget for a few moments that I ever had them.

In 1865, the great landscape architect Frederick Law Olmsted, designer of New York City’s Central Park, looked out over Yosemite Valley and was so moved that he urged the California legislature to protect it from development. “It is a scientific fact,” he wrote, “that the occasional contemplation of natural scenes of an impressive character … is favorable to the health and vigor of men.”

Olmsted’s claim had a long history, going back at least to Cyrus the Great, who some 2,500 years ago built gardens for relaxation in the busy capital of Persia. Paracelsus, the 16th-century German-Swiss physician, wrote, “The art of healing comes from nature, not from the physician.” And 19th-century Americans Ralph Waldo Emerson and John Muir built the case for creating the world’s first national parks by claiming that nature had healing powers for both mind and body. There wasn’t hard evidence back then.

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There is now.

Researchers from the University of Exeter Medical School in En­gland analyzed data from 10,000 city dwellers and found that those living near more green space reported less mental distress, even after adjusting for income, marital status, and employment (all of which are correlated with health). In 2009, Dutch researchers found a lower incidence of 15 diseases—including depression, anxiety, and migraines—in people who lived within about a half-mile of green space. Richard Mitchell, an epidemiologist and a geographer at the University of Glasgow in Scotland, found fewer deaths and less disease in people who lived near green spaces, even if they didn’t use them. “Our own studies plus others show these restorative effects whether you’ve gone for walks or not,” Mitchell says. People who have window views of trees and grass have been shown to recover faster in hospitals, perform better in school, and display less violent behavior.

Japanese researchers led by Bum Jin Park and Yoshifumi Miyazaki at Chiba University quantified nature’s effects on the brain by sending 280 subjects for a stroll in 24 different forests while the same number of volunteers walked around city centers. The forest walkers hit the anti­-anxiety jackpot, showing a 16 percent decrease in the stress hormone cortisol. From fMRI experiments, ­South Korean researchers found that the brains of volunteers looking at city scenes showed more blood flow in the amygdala, which processes fear and anxiety. In contrast, natural scenes lit up the anterior cingulate cortex and the anterior insula—areas associated with empathy and altruism. Miyazaki believes our minds and bodies relax in natural surroundings because our senses adapted to interpret information about plants and streams, he says, not traffic and high-rises.

And yet less than a quarter of American adults say they spend 30 minutes or more outside every day. “People underestimate the happiness effect” of being outdoors, says Lisa Nisbet, an assistant professor of psychology at Canada’s Trent University. “We don’t think of it as a way to increase happiness. We think other things will, like shopping or TV,” she adds. “We evolved in nature. It’s strange we’d be so disconnected.”

Nooshin Razani, MD, at UCSF ­Benioff Children’s Hospital in Oakland, California, is one of several doctors around the world starting to counter this disconnection as a means to heal the anxious and depressed. As part of a pilot project, she’s training pediatricians in the outpatient clinic to write prescriptions for young patients and their families to regularly visit verdant parks nearby, with transportation provided in partnership with the East Bay Regional Parks District. To guide the physicians and patients into a mind-set where this makes sense as treatment, she says, “we have transformed the clinical space so nature is everywhere. There are maps on the wall, so it’s easy to talk about where to go, and pictures of local wilderness.”

In some countries, nature is woven into the government’s official mental health policy. At the Natural Resources Institute Finland, the nation’s high rates of depression, alcoholism, and suicide led a research team to recommend a minimum nature dose of five hours per month in an effort to improve the nation’s mental health. “A 40- to 50-minute walk seems to be enough for physiological changes and mood changes and probably for attention,” says Kalevi Korpela, a professor of psychology at the University of Tampere. He has helped design half a dozen “power trails” that encourage mindfulness and reflection. No-­nonsense signs say things like “You may squat down and feel a plant.”

At the healing forest in the Saneum Natural Recreation Forest in South Korea, a government employee known as a “forest healing instructor” offers me elm-bark tea, then takes me on a hike along a creek, through shimmering red maples, oaks, and pine trees. We come upon a cluster of wooden platforms arranged in a clearing. Forty firefighters with post-traumatic stress disorder are paired off on the platforms as part of a government-sponsored three-day healing program. Among them is Kang Byoung-Wook, a 46-year-old from Seoul. He recently returned from a big fire in the Philippines, and he looks exhausted. “It’s a stressed life,” he says. “I want to live here for a month.”

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In industrial Daejeon, the ­South Korean forest minister, Shin Won-Sop, a social scientist who has studied the effects of forest therapy on alcoholics, tells me that human well-being is now a formal goal of the nation’s forest plan. Thanks to the new policies, visitors to South Korea’s recreation forests increased from 9.4 million in 2010 to 12.8 million in 2013. “Of course, we still use forests for timber,” Shin says. “But I think the health area is the fruit of the forest right now.”

His ministry has data suggesting that forest healing reduces medical costs and benefits local economies. What’s still needed, he says, is data on specific diseases and on the specific natural qualities that make a difference. “What types of forests are more effective?” Shin asks.

My own city brain, which spends much of the year in Washington, DC, seems to like the Utah wilderness very much. By day, we hike among flowering prickly pear cacti; by night, we sit around the campfire. Strayer’s students seem more relaxed and sociable than they do in the classroom, he says, and they give much more persuasive presentations.

His research, which centers on how nature improves problem-solving, builds on the theory that nature’s ­visual elements—sunsets, streams, and butterflies—are what reduce stress and mental fatigue. Fascinating but not demanding, such stimuli promote a soft focus that allows our brains to wander, rest, and recover.

A few months after our Utah trip, Strayer’s team sends me the results of my EEG test. The colorful graph shows my brain waves at a range of frequencies and confirms that the gentle fascination of the San Juan River succeeded in quieting my prefrontal cortex. Compared with samples from research subjects who had stayed in the city, my theta signals were lower.

So far, the other research subjects’ results also confirm Strayer’s hypothesis. But no study can offer a full explanation of the brain-on-nature experience; something mysterious will always remain, Strayer says, and perhaps that’s as it should be. “At the end of the day,” he says, “we come out in nature not because science says it does something to us but because of how it makes us feel.” Next, check out the benefits of walking outside for just 15 minutes.