Measuring Biophysical and Psychological Stress Levels Following Visitation to Three Locations with Differing Levels of Nature

Summary

The purpose of this paper is to identify changes in stress levels after visitation to three different settings and to describe the methods used in identifying stress levels based on measures of salivary cortisol, α-amylase, and a psychological self-report instrument. 

Abstract

Visitation to natural environments has been linked to psychological stress reduction. Although most stress-related research has relied on self-report formats, a growing number of studies now incorporate biological stress-related hormones and catalysts, such as cortisol and α-amylase, to measure levels of stress. Presented here is a protocol to examine the effects on levels of biophysical and psychological stress following visitation to three different locations with differing levels of nature. Biophysical and self-reported psychological stress levels are measured immediately upon entering the selected locations and just prior to the visitors leaving the site. Using a "drool" method, the biophysical measure consists of 1-2 mL samples of saliva provided by study subjects upon entry to one of three study locations. As prescribed by extant literature, the saliva is collected within a 45 minute time frame following the end of the visitor’s engagement at the location. Following saliva collection, the samples are labeled and transported to a biological lab. Cortisol is the biophysical variable of interest in this study and measured using an ELISA process with a TECAN plate reader. To measure self-reported stress, the Perceived Stress Questionnaire (PSQ), which reports levels of worry, tension, joy, and perceived demands. Data are collected at all three sites in the late afternoon through early evening. When compared across all three settings, stress levels, as measured by both the biological markers and self-reports, are significantly lower after visitation to the most natural setting.

Introduction

Elevated stress levels have long been linked to many serious health conditions such as heart disease, obesity, and psychological disorders^1,2,3. A growing body of research suggests that close proximity or visitation to natural settings such as park and non-developed landscapes can have a remarkable effect on psychological well-being and decreased levels of stress^{1,4,5,6,7,8,<....}

Protocol

This study follows the policies and guidelines of Human Research Protection Program of Indiana University Institutional Review Board.

1. Location selection

1. Select the number of sites (n) based on different levels of nature.
   NOTE: We chose three sites for our work. Using a continuum based on levels of "naturalness", Site A was considered the most natural and is comprised of approximately 1,200 acres of wooded ridges bordering a lake and set within a deciduous forest. The most common activities include walking and wildlife watching. Site B was a 33-acre municipal park featuring walking paths, places for gatherings, playground....

Results

Sample Description
Utilizing a quota sampling technique, this study recruited 35 visitors from each of the three sites. In total, 105 subjects were recruited in this study, including 63 males and 42 females. Average ages of visitors recruited from three different sites were 25.9 years (Site A), 37.2 years (Site B), and 28.8 years (Site C). Frequencies of subjects' visitation to the selected three sites were also recorded. For Site A and Site C, the majority of subjects visited this site one to three .......

Discussion

The aim of this study is to identify potential changes in stress using biophysical and psychological instruments following recreational visitation to three different settings with different levels of nature. Both cortisol and α-amylase have been shown to be reliable indicators of levels of psychological stress. The amylase assay procedure described in this study has been adapted to a 96 well format. When amylase levels in saliva are high, absorbance changes occur rapidly. Therefore, it is critical to limit the numbe.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Cortisol Enzyme Immunoassay Kit	DetectX	K003-H1	The Cortisol Enzyme Immunoassay kit is designed to quantitatively measure cortisol present in dried fecal extracts, saliva, urine, serum, plasma and culture media samples.
Cryogenic Labels for Cryogenic Storage	Fisherbrand	5-910-A	Unique adhesive withstands extreme temperature
Liquid Amylase (CNPG3) Reagent Set	Pointe Scientific	A7564	For the quantitative kinetic determination of α-amylase activity in human serum.
Round Bottom 2mL Polypropylene Tubes with External Thread Cap	Greiner Bio-One	07-000-257	2.0 ml U-BTM Cryo.s self standing polypropylene sterilized
Synergy Multi-Mode Microplate Reader	BioTek		It is a single-channel absorbance, fluorescence, and luminescence microplate reader that uses a dual-optics design to perform measurements of samples in a microplate format.