• Stress reduction through contact with nature is well established, but far less is known
    about the contribution of contact parameters – duration, frequency, and nature quality.
    This study describes the relationship between duration of a nature experience (NE), and
    changes in two physiological biomarkers of stress – salivary cortisol and alpha-amylase.
    It is the first study to employ long-term, repeated-measure assessment and the first
    evaluation wherein study participants are free to choose the time of day, duration, and
    the place of a NE in response to personal preference and changing daily schedules.
    During an 8-week study period, 36 urban dwellers were asked to have a NE, defined as
    spending time in an outdoor place that brings a sense of contact with nature, at least
    three times a week for a duration of 10 min or more. Their goal was compliance within
    the context of unpredictable opportunity for taking a nature pill. Participants provided
    saliva samples before and after a NE at four points over the study period. Before-NE
    samples established the diurnal trajectory of each stress indicator and these were in line
    with published outcomes of more closely controlled experiments. For salivary cortisol,
    an NE produced a 21.3%/hour drop beyond that of the hormone’s 11.7% diurnal drop.
    The efficiency of a nature pill per time expended was greatest between 20 and 30 min,
    after which benefits continued to accrue, but at a reduced rate. For salivary alphaamylase,
    there was a 28.1%/h drop after adjusting for its diurnal rise of 3.5%/h, but
    only for participants that were least active sitting or sitting with some walking. Activity
    type did not influence cortisol response. The methods for this adaptive management
    study of nature-based restoration break new ground in addressing some complexities
    of measuring an effective nature dose in the context of normal daily life, while bypassing
    the limitations of a clinical pharmacology dose–response study. The results provide a
    validated starting point for healthcare practitioners prescribing a nature pill to those
    in their care. This line of inquiry is timely in light of expanding urbanization and rising
    healthcare costs.

  • School for Environment and Sustainability, University of Michigan, Ann Arbor, MI, United States



    Copyright: Copyright © 2019 Hunter, Gillespie and Chen. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).

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