http://www.pnas.org/content/112/28/8567.abstract
- Gregory N. Bratmana,1,
- J. Paul Hamiltonb,
- Kevin S. Hahnc,
- Gretchen C. Dailyd,e,1, and
- James J. Grossc
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Contributed by Gretchen C. Daily, May 28, 2015 (sent for review March 9, 2015; reviewed by Leslie Baxter, Elliot T. Berkman, and Andreas Meyer-Lindenberg)
Significance
More than 50% of people now live
in urban areas. By 2050 this proportion will be 70%. Urbanization is
associated with increased
levels of mental illness, but it’s not yet
clear why. Through a controlled experiment, we investigated whether
nature experience
would influence rumination (repetitive
thought focused on negative aspects of the self), a known risk factor
for mental illness.
Participants who went on a 90-min walk
through a natural environment reported lower levels of rumination and
showed reduced
neural activity in an area of the brain
linked to risk for mental illness compared with those who walked through
an urban
environment. These results suggest that
accessible natural areas may be vital for mental health in our rapidly
urbanizing
world.
Abstract
Urbanization has many benefits,
but it also is associated with increased levels of mental illness,
including depression. It
has been suggested that decreased nature
experience may help to explain the link between urbanization and mental
illness.
This suggestion is supported by a growing
body of correlational and experimental evidence, which raises a further
question:
what mechanism(s) link decreased nature
experience to the development of mental illness? One such mechanism
might be the impact
of nature exposure on rumination, a
maladaptive pattern of self-referential thought that is associated with
heightened risk
for depression and other mental illnesses.
We show in healthy participants that a brief nature experience, a
90-min walk in
a natural setting, decreases both
self-reported rumination and neural activity in the subgenual prefrontal
cortex (sgPFC),
whereas a 90-min walk in an urban setting
has no such effects on self-reported rumination or neural activity. In
other studies,
the sgPFC has been associated with a
self-focused behavioral withdrawal linked to rumination in both
depressed and healthy
individuals. This study reveals a pathway
by which nature experience may improve mental well-being and suggests
that accessible
natural areas within urban contexts may be
a critical resource for mental health in our rapidly urbanizing world.
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