Historically, a remedy for low spirits would be to send someone to the quiet of the country or seashore. The popularity of vacations to national parks, camping, and even local breaks for a picturesque walk in a local greenspace to clear the mind would speak to empirical evidence that nature does soothe the savage beast. And recently, scientists have been studying the idea of nature therapy with a bit more rigor than a dashed-off prescription for a hike.
We are now far removed from the natural world of our ancestors. More than 50 percent of people live in urban areas. Increased urbanization is associated with increased levels of mental illness, particularly anxiety and depression. Growing up in a rural setting correlates with a less acute stress response, and exposure to greenspace significantly correlates to a positive effect on well-being in a large two-decade study.
There are many studies showing a similar relationship between nature exposure, relaxation, and well-being. But how does exposure to green space help us relax and unwind, exactly?
Dr. Gregory Bratman’s group at Stanford has published a couple of papers following a small group of healthy volunteers told to go for a five-kilometer walk in the San Francisco Bay area. Half walked along a busy street while the other half went for a scenic walk with beautiful views of the mountains and the bay. The nature walk resulted in decreased anxiety, rumination, and negative feelings, and even increased performance on cognitive tests compared to the walk along a busy street. Later, the same researchers did MRIs and measured blood flow in brain areas of healthy people who went on a 90-minute walk in the same urban vs. more natural setting. They found that the nature walkers had reduced activity in a particular brain region, the subgenual prefrontal cortex. This area of the brain is associated with rumination, or worrying on the same issues over and over, a problem described often in depressive and anxiety disorders or thoughts of suicide.
Japanese researchers have long been interested in so-called forest therapy for a variety of physical and mental ailments, and they too have been studying brain functioning and exposure to nature. Ryota Sakurai’s group published a paper looking at PET scans of older adults. Those who reported going out less frequently had higher depression scores and lower activity scores of the orbital prefrontal cortex of the brain.