By Eva M. Selhub and Alan C. Logan. December 2015/January 2016
Scientific research provides powerful evidence of the importance of
nature for our health. Time spent in the Great Outdoors reduces the
stress hormone cortisol and increases our sense of well-being.
As
Western society has developed, we have retreated from the Great
Outdoors, placing greater importance on technological pursuits and human
creations. Mounting scientific evidence reveals that by pushing
ourselves away from nature, we not only have distanced ourselves from
crisis-level environmental problems, but also have begun to lose contact
with a vital mental-health tool. By denying ourselves time in green
space, we risk rejecting an essential part of our heritage — a truth
that, ironically, we are now able to see more clearly because of
advances in medical technology.
The Science of Green Space
Healers
within various medical systems, from India’s Ayurvedic medicine to
traditional Chinese medicine, have long advocated for the importance of
nature. Indeed, in many cultures, it’s regarded as a form of medicine.
But the notion that trees and flowers can influence psychological
well-being remained largely untested in a scientific way until 1979,
when behavioral scientist Roger S. Ulrich examined the mental influence
of nature scenes on stressed students. His psychological testing showed
differences in mental states and outlooks after the students viewed
various environmental scenes. The nature scenes increased positive
feelings of affection, playfulness, friendliness and elation. Urban
views, on the other hand, significantly cultivated one emotion in these
students: sadness. Viewing nature tended to reduce feelings of anger and
aggression, and urban scenes tended to increase these feelings.
Encouraged
by his findings, Ulrich set up a similar experiment to measure brain
activity in unstressed, healthy adults. His team discovered that seeing
natural landscapes was associated with increased production of
serotonin, a chemical that operates within the nervous system. Almost
all antidepressant medications are thought to work by enhancing the
availability of serotonin for use in nerve cell communication, hence its
moniker, “the happy chemical.” A follow-up study showed that green
spaces acted as a sort of visual Valium: The nature scenes fostered
positive thoughts, and lowered post-stress anger and aggression.
Many other contemporary researchers have used objective testing to support Ulrich’s pioneering work:
•
In one study, older adults in a residential care center in Texas
engaged in the same mental activities in two contexts — once in a garden
setting and again in an indoor classroom. The participants were shown
to produce lower levels of the stress hormone cortisol while in the
garden.
• The presence of plants in a room, particularly flowering plants, can
enhance recovery from the stress induced by an emotional video, quickly
bringing brain wave activity back to normal, researchers at Kansas State
University found.
• A research group from Taiwan reported that rural farm scenes are
associated with higher alpha-wave activity, particularly in the right
part of the brain, which has been linked with creativity. Forest scenes
and natural water scenes promote alpha-wave activity and decrease heart
rate. Conversely, an increase in muscular tension has been associated
with city scenes.
Shinrin-Yoku – Forest Bathing
Among
the many reasons to preserve what’s left of our forests, the mental
aspects stand tall. In 1982, the Forest Agency of the Japanese
government premiered its shinrin-yoku plan. In Japanese, shinrin means
forest, and yoku refers here to “basking in.” More broadly, it is
defined as “taking in, with all of our senses, the forest atmosphere.”
In 1990, Dr. Yoshifumi Miyazaki of Chiba University conducted a small
test study of shinrin-yoku in the beautiful landscape of Yakushima, home
to Japan’s most revered forests. Miyazaki found lower levels of the
stress hormone cortisol in subjects after they took forest walks,
compared with those who took walks in the controlled environment of the
laboratory.
Since then, university and government researchers in
Japan have collaborated on detailed investigations, including projects
to evaluate physiological markers while subjects spend time among trees.
These studies have confirmed that spending time in a forest setting can
reduce psychological stress, depressive symptoms and hostility, while
at the same time improving sleep, and increasing vigor and a feeling of
liveliness. These subjective changes match objective results reported in
nearly a dozen studies — that lower blood pressure, pulse rates and
levels of cortisol accompany time spent amid trees and flowers.
Stress
hormones can compromise our immune systems, particularly the activities
of front-line defenders, such as antiviral killer cells. Because
forest-basking can lower stress-hormone production and elevate mood,
it’s not surprising that it also influences immune-system strength.
The Practical Necessity of Nature Scenes
In 1984, Ulrich published a landmark study in the prestigious journal Science,
in which he examined records for adults who had undergone identical
gallbladder surgeries in the same hospital. The only major distinction
among the patients was the room into which they were wheeled for
recovery. Rooms on one side of the hospital had windows with a view to a
mini-forest, while rooms on the other side offered a radically
different vista of red bricks. The results were quite dramatic: Those
who had an outdoor view of trees had significantly shorter hospital
stays, fewer post-surgical complaints, and were able to manage their
pain with aspirin instead of narcotics. Other studies have confirmed
Ulrich’s findings. Among them:
• Norwegian research showed that
having a plant at or within view of an office workstation significantly
decreases the amount of sick leave workers take.
• Research published in 2008 in the Journal of the Japanese Society for Horticultural Science
showed that greening select high school classrooms with potted plants
significantly reduced the students’ visits to the school’s infirmary
compared with the number of visits by students attending classes in
rooms without plants.
World
Health Organization projections indicate that in fewer than 20 years,
75 percent of the world’s population will live in urban settings,
compared with the current distribution of about 54 percent city
dwellers. The potential ability of a single factor — time in nature — to
counteract a cascade of stress hormones will have enormous implications
for us and future generations.
Because so many aspects of human
health and even longevity are negatively influenced by stress, it
follows that green space is a promoter of human health, vitality and
longevity. Ample research confirms this. The closer your family lives to
green space, the healthier you’re likely to be, and the longer you’re
likely to live. Merely being in nature for brief periods — even just
having it in view — can reduce the flood of stress hormones and improve
immune defenses.
Your Brain on Nature
Critics once might
have suggested that subjects who reported improved mood while viewing
nature scenes were merely marking the right boxes that would fulfill the
researchers’ expectations. The true, objective test would be the
ability to go inside the brain and analyze it while it was focused on
nature.
In the 1990s, researchers in California gained that
ability by using functional magnetic resonance imaging (fMRI), a
sophisticated brain-imaging technique. Their findings showed that
aesthetically pleasing nature views fired up a specific portion of the
brain that’s rich in opioid receptors. These receptors connect to the
brain cells within the dopamine reward system, and carry the potential
to trigger feelings of wellness and to propel the motivation required
for positive behavior.
This was an incredible finding, revealing
that nature is like a little drop of morphine for the brain. Although
best known for pain inhibition, the opioid receptors do so much more.
When these receptors are activated, people are less likely to perceive
themselves as stressed, are more likely to form emotional bonds, and
tend to dwell less on negative memories.
In two separate studies,
Korean researchers used imaging to assess brain-activation patterns
while subjects viewed urban or nature-based scenery. In the first study,
viewing the urban scenes resulted in pronounced activity in the
amygdala, a center in the brain most often associated with feelings of
fear. Overactivity of this center has been linked to impulsivity and
anxiety. Furthermore, chronic stress and cortisol may promote activity
in the amygdala, and in this overactive state, we tend to selectively
prioritize the memorization of negative events and experiences. This
becomes a vicious cycle: The world looks a bit more scary and
depressing, and our dominant memories confirm that to be true. When the
amygdala is amped-up on a regular basis, it fuels the brain’s fear. The
good news is that we can regain control by acknowledging our thought
processes and seeing green — placing ourselves in environments that will
dial down the fear.
When
large population studies indicating a stress-buffering effect are
layered on top of studies using subjective and objective evaluations of
mood and stress — and when this information is, in turn, layered onto
hospital data and brain-imaging studies — the picture of nature’s
influence emerges. Add to this body of information dozens of
forest-basking studies from Japan, the argument that time in nature has
no consequence on human health and physiology becomes impossible to
support.
The results of these scientific investigations should
wake all of us up to the importance of preserving nature. The wellness
of individuals and nations — and clearly the planet — depends on
recognizing the importance of nature to human health.
Research
has shown that pleasure and happiness are elevated as tree density
increases. The bigger and denser the trees, the better the scenic beauty
scores — up to a point. If trees are too tightly packed — if a trail is
too narrow or obscured — the scene becomes foreboding and causes fear.
Lining
one’s walls with wood might be too much of a good thing. Japanese
researchers have found that the sweet spot for the right amount of wood
on the floor and walls is somewhere between 30 and 40 percent of surface
area. If you go all-out and panel the entire room, your stress can
actually increase.
