Beil K, Hanes D. The influence of urban natural and built environments on physiological and psychological measures of stress—a pilot study. Int J Environ Res Public Health. 2013 Mar 26;10(4):1250-1267.
Pilot study using a crossover experimental design to investigate the effect of four urban environments on physiological and psychological stress measures.
Fifteen healthy participants (8 male, 7 female) between the ages of 20 and 61 years. Participants were screened for endocrine and/or psychiatric conditions.
Measurements of salivary amylase and salivary cortisol were collected from subjects before and after visiting locations for 20-minute increments. The locations visited were divided into “very natural, mostly natural, mostly built, and very built” with varying levels of “natural” atmosphere, ranging from a rural park setting to an urbanized outside shopping mall. Trending of salivary amylase and cortisol, measures of physiologic stress, were elevated after visiting the more urban settings. Conversely, stress perception by participants (Perceived Stress Scale and Perceived Restorativeness Scale) was statistically significantly lower in the “very natural” setting versus the “mostly urban” setting.
The concept that nature provides stress relief gained momentum during the early 19th century when Henry David Thoreau and Ralph Waldo Emerson, among others, began the transcendentalist movement. The proponents of this belief system encouraged people to find “an original relation to the universe” through spending time alone in nature.1 Past research has illustrated the many benefits of spending time in “greener” settings. Children seem to be particularly drawn to wooded areas more frequently than barren spaces, and the quality of their play appears to be more creative in these environments. This would certainly make sense when looking deeper into the research.
In 1989, the Kaplans from the University of Michigan wrote a book called The Experience of Nature: A Psychological Perspective.2 The authors coined the term Attention Restoration Theory, which suggests that the mechanism prone to becoming fatigued (voluntary attention) after prolonged or intense use of directed attention can be renewed by contact with nature. In fact, children with attention deficit disorder show an improvement in their symptomology when spending time in nature,3 and spending a mere 20 minutes in a park was as effective in reducing attention problems as some formulations of methylphenidate.4 This last piece of evidence is particularly impressive, as 20 minutes is quite a small fraction of the day. It is unfortunate that recess is often viewed as an extraneous factor in a young student’s daily activities when in fact it may be the very thing that would improve scholastic performance.
Dr. Beil’s research is yet another piece of evidence that supports what we know are the effects of spending time in natural settings. My comments are largely based on a conversation with third- and fourth-year medical students on a rotation who were assigned to read and discuss this paper. The first idea was the population demographics of the participants, which was noted by the authors. Portland, Ore., is a particularly unique city in that it has repeatedly been touted as one of the fittest towns in the country,5 so it would make sense that many participants from Portland who are subjects in a research study would report enjoyment and a sense of better well-being in more natural spaces. It is no surprise that the Perceived Stress Scales of the participants were lower than the 2009 national mean as Portland is hailed as a “green” city in general. In discussing this with medical students, comments surfaced that were related to the fact that participants had to shut their phones off during time in the study, and this could certainly have contributed to feelings of relaxation. Another consideration is the differences in environments that the subjects were exposed to: pictures included in the paper showed that they were not drastically diverse. However, this may lend more validity to the slight intricacies in one’s environment and the power of nature. As far as extraneous factors, the participants were told to eliminate drug and alcohol use for 24 hours, but residual effects may still influence perceptions of environment in varying settings.
The most interesting discovery however, regardless of the small number participants, was the overwhelming difference between how males and females responded to their environments. It seems that females were much more sensitive than the males to their settings, which reinforced findings from other studies. Factors such as concerns with personal safety or simply just gender differences in emotional processing may very well play a role in these differences. Overall, this study was well designed and showed us once again that only a brief amount of time spent in greener spaces can have powerful effects on our physiology and psychological well-being.
There were several limitations of this study. The design was to assess a “within subject methodology for measuring urban environmental settings effect on stress.” Only 2 time points were assessed, limiting the data points for cortisol and amylase. Extraneous noises, happenings, and variability of the atmosphere could not be controlled for and did affect participants’ experience as reported by participants. The measures of Perceived Stress Scale and Perceived Restorativeness Scale are not validated means of assessment. Future studies may use more validated scales for assessment. Lastly, this population had a lower baseline score for stress; thus, changes in stress would be more limited than in a highly stressed population.