How Walking in Nature Changes the Brain

These days most of us live in cities, and spend far less time outside in green, natural spaces than people did several generations ago. But maybe we should be heading to the park more frequently. According to a new study, walking in nature soothes the mind and, in the process, changes the workings of our brains in ways that improve our mental health.

Various studies have found that urban dwellers with little access to green spaces have a higher incidence of psychological problems than people living near parks; and city dwellers who visit natural environments have lower levels of stress hormones immediately afterward than people who have not recently been outside.

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Gregory Bratman, a graduate student at Stanford University wanted to examine the neurological mechanisms underlying the effects of being outside in nature. The study, which was published last week in Proceedings of the National Academy of Sciences , looked at what effect a walk might have on a person’s tendency to brood.

Brooding—a mental state probably familiar to most of us—is when we incessantly ruminate over the ways in which things are wrong with ourselves and our lives. This broken-record fretting is not healthy or helpful. It can be a precursor to depression and is disproportionately common among city dwellers compared with people living outside urban areas, studies show. Brooding is also is strongly associated with increased activity in a portion of the brain known as the subgenual prefrontal cortex.

Bratman and his colleagues gathered 38 healthy, adult city dwellers and asked them to complete a questionnaire to determine their normal level of brooding. The researchers also checked for brain activity in each volunteer’s subgenual prefrontal cortex, using scans that track blood flow through the brain. Greater blood flow to parts of the brain usually signals more activity in those areas.

Then the scientists randomly assigned half of the volunteers to walk for 90 minutes through a leafy, quiet, park-like portion of the Stanford campus or next to a loud, hectic, multi-lane highway in Palo Alto. The volunteers were not allowed to have companions or listen to music. They were allowed to walk at their own pace.

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Immediately after completing their walks, the volunteers returned to the lab and repeated both the questionnaire and the brain scan.

As one might have expected, walking along the highway had not soothed people’s minds. Blood flow to their subgenual prefrontal cortex was still high and their broodiness scores were unchanged.

But the volunteers who had strolled along the quiet, tree-lined paths showed slight but meaningful improvements in their mental health, according to their scores on the questionnaire. They were not dwelling on the negative aspects of their lives as much as they had been before the walk. They also had less blood flow to the subgenual prefrontal cortex; that portion of their brains were quieter.

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According to Bratman: These results “strongly suggest that getting out into natural environments” could be an easy and almost immediate way to improve moods for city dwellers.”

There’s still much to be studied, including how much time in nature is sufficient? Is it the greenery, quiet, sunniness, or something else that lifts our moods? Do we need to be walking outside to gain the fullest psychological benefits?

But in the meantime, Bratman pointed out, there is little downside to strolling through the nearest park, and some chance that you might beneficially muffle, at least for awhile, your subgenual prefrontal cortex.

Curated Article and Photo Credit from The New York Times