“When we walk, we naturally go to the fields and woods: What would become of us, if we walked only in a garden or a mall?” wrote Henry David Thoreau in The Atlantic in 1862.
Thoreau extolled (and extolled and extolled—the piece was more than 12,000 words long) the virtues of walking in untamed environments. In the decades since, psychologists have proved him right. Exposure to nature has been shown repeatedly to reduce stress and boost well-being.
But scientists haven’t been sure why. Does it have to do with the air? The sunshine? Some sort of evolutionary proclivity toward green-ness?
A group of researchers from Stanford University thought the nature effect might have something to do with reducing rumination, or as they describe it, “a maladaptive pattern of self-referential thought that is associated with heightened risk for depression and other mental illnesses.” Rumination is what happens when you get really sad, and you can’t stop thinking about your glumness and what’s causing it: the breakup, the layoff, that biting remark. Rumination shows up as increased activity in a brain region called the subgenual prefrontal cortex, a narrow band in the lower part of the brain that regulates negative emotions. If rumination continues for too long unabated, depression can set it.