Nature exposure is known to have a positive influence on stress reduction. What's not clear, however, is the amount and form a nature experience (NE) should be to achieve maximum effect. This study addresses this issue by investigating the relationship between duration of a nature experience (NE) and changes in two physiological indicators of stress: salivary cortisol and salivary alpha-amylase. By using both of these biomarkers of stress, the researchers were able to separate the nature exposure effect from the natural shift in the production of cortisol and alpha-amylase over the period of the day. Salivary cortisol is highest in the morning and then drops during the day. Amylase drops in the first hour after waking and steadily increases during the day. Both cortisol and amylase respond to physical and psychological stressors and can thus be used to quantify the change in an individual's physiological stress. This study aimed to articulate a “nature prescription” that healthcare providers could use as an inexpensive preventive treatment for mental well-being that would be effective in everyday settings.
This study was conducted over a period of eight weeks and was based on data provided by 36 urban residents. Participants were asked to spend at least ten minutes in an outdoor place that provided a sense of contact with nature at least three times a week over the eight-week period. They were free to choose the time of day, the duration (as long as it was 10 minutes or longer), and the place of a NE. This flexibility allowed participants to structure their NE around personal preference and changing daily schedules. Participants provided saliva samples before and after a NE four different times during the study period. Participants also provided a log of their NEs which included time of day, duration of NE, and type of activity during the NE (sitting, walking, sitting and walking).
Results showed that a NE was effective in reducing stress as measured by both saliva cortisol and amylase. The “nature pill” (NE) was most effective when the NE lasted 20 – 30 minutes. This study has important implications for healthcare providers by providing a realistic estimate of effective dose of NE for reducing stress. Results showed that even a relatively short NE in an urban environment integrated within the context of everyday life can be effective in stress reduction.
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