Staying positive is a walk in the park, according to new research (paywall) on the mental health benefits of spending time outside. A stroll in nature was found to draw the brain's attention away from distressing, embarrassing or upsetting thoughts.

"Nature affects the way you … allocate your attention," helping people not only feel better, but also think better thoughts, said Greg Bratman, the study's lead author and a PhD candidate at Stanford University. Using brain scans and participant surveys, his team showed that a 90-minute walk in nature reduced a type of negative thinking that's linked to depression and other mental illnesses.

Bratman emphasized the study's value for urban planners, noting that cities need to make room for parks and trees in order to protect citizens' mental health. Other nature researchers said the findings should influence the behavior of individuals, motivating people to make time for all kinds of outdoor fun.

"There's no question that a walk in nature is really, really good for us," said Linda Buzzell, a psychotherapist who founded the International Association for Ecotherapy. "But people have preferences for the kind of nature connection that excites them."

Nature versus urban jungle

As a California native, Bratman's love of nature runs deep. His parents took him on backpacking trips throughout his childhood, and he continues to prioritize time in nature, especially now that he's a dad.

The new study combined his personal interests with his academic pursuits, he said, noting, "I'm trying to add to the growing conversation" about nature's ability to boost people's mood.

Several recent studies, such as one from a team of University of Melbourne researchers (paywall) that showed just looking at photos of trees and plants improved people's focus and performance, have confirmed what outdoor enthusiasts like Bratman already knew: Spending time in nature is an essential part of both mental and physical wellness.

And yet it remains unclear exactly how a dose of trees and sunshine affects the body and brain, Bratman said. His team wanted to explore the mechanism by which time in nature promotes mental health.

"We asked, 'What's changing about the way we regulate our emotions when we're in different environments?,'" Bratman said.

In the study, 38 participants, none of whom had ever been diagnosed with a mental illness, went on a 90-minute walk, half in an urban green space near Stanford's campus and half on a sidewalk along one of Palo Alto's busiest streets.

Before and after the trip, participants sat for brain scans and completed a questionnaire about the way they process daily events, assessing their ability to shut off negative thoughts about themselves and how often they rehearse embarrassing or disappointing moments.

Both the scans and the surveys targeted what psychologists call rumination, or repetitive negative thoughts about the self that are associated with increased risk to develop mental disorders like depression.

Researchers found that nature's positive impact on mental health is explained, at least in part, by its ability to decrease rumination. People in the nature group rated themselves better on the questionnaire after the walk, and their brain scans showed less activity in the area of the brian associated with maladaptive thinking compared to those who had strolled along a busy street.

"We showed that the walk shifted patterns of thought, not just (participants') present mood," Bratman said.

Eva Selhub, a physician and co-author of "Your Brain on Nature," said the results illustrate the importance of stimulating the brain with lush, green scenery. Views of bustling city streets or cranky coworkers do little for an organ designed to take in stimuli like rustling grass and chirping birds.

"When you go out in nature, you're raising serotonin, dopamine and endorphin levels," which are associated with a good mood, she said. "(Time in nature) leads to improved health and an improved outlook."

Reacting to the research

Although the study's small sample size means more work needs to be done to explain the relationship between the great outdoors and mental well-being, Bratman said he's hopeful that the findings will urge policymakers and urban planners to take the value of green space seriously.

"We shouldn't gobble up open space without thinking about the mental health repercussions for even the people who just drive by it," he said.

The new research also holds valuable lessons for individuals, Selhub noted.

"When you get stressed, you can take advantage of (this research)," she said. Spending time in nature "is one of those things you can do for yourself to improve your outlook and energy level."

Just as individuals might pack a few extra snacks in their work bag to prepare for a long day of meetings, people should schedule a walk in the park or on the beach to follow difficult conversations or performance reviews, Selhub added, noting that "it's good for people to live with intention."

Similarly, Buzzell described the study as an opportunity to reflect on how all of us could spend more time outside, although she cautioned that a walk won't be the best option for everyone.

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"For one person, a walk would be a wonderful (ecotherapy) prescription. But for someone else, the best answer might be something like connecting with an animal companion," she said.

Buzzell encourages her clients to find outdoor hobbies that get them excited to spend time in nature. In that way, they can enjoy the mental health benefits and have fun, too.

"You have to find what works best for you to get your dose of 'vitamin N,'" she said.

Email: kdallas@deseretnews.com Twitter: @kelsey_dallas