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OpenTrials
Completed

NCT Number: NCT05316597

Do Terpenes Play a Role in the Stress-reducing Effects of a Forest Bathing Intervention?

This pilot study evaluates the role terpenes play in the stress-reducing effects of a forest bathing intervention. Participants will participate in two interventions in random order: 1) terpene exposure and 2) no terpene exposure.

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Key information

Conditions

Monoterpene Exposure During a Forest Bathing Intervention

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Pack Forest

Eatonville, Washington, 98328, United States

About this study

The investigators will use an individual-level crossover design in which each session is conducted independently and on different days. Participants will be outfitted with a powered air purifying respirator (PAPR) to selectively modulate exposure to a natural suite of forest-derived volatile organic compounds (VOCs) while present in forest environments. Each participant will undergo two forest bathing sessions, one in which VOCs are not filtered (treatment condition), and one in which they are filtered (control condition). Sessions will be separated by a washout period of at least 8 days for each participant, and order will be counterbalanced. The investigators will estimate the average effect of treatment over 40 distinct treatment days against 40 distinct control/filtered days. The power and sample size calculations (N = 40) were determined using previous nature exposure studies of similar cross-over design. The study is adequately powered assuming the conventional targets of α = 0.05 and β = 0.80 with a 10% anticipated dropout rate, and including temperature, wind, and light variability during treatment days.

The specific aim of this project is to 1) assess whether VOC inhalation regulates increases in the high frequency (HF) (ms2) component of heart rate variability (HRV) as the primary outcome (with decreases in blood pressure, heart rate, self-reported stress, and levels of inflammatory cytokines in serum included as secondary outcomes); and 1a) assess the degree of association of absorbed dose of six forest-derived VOCs (i.e., α-pinene, β-pinene, β-myrcene, Δ-3-carene, limonene, β- carophyllene) in serum with these outcomes.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • 18 years and older
  • Non-smoker
  • Physically capable of walking for approximately 15-20 min from the study vehicle to the clinic and experimental locations.

Exclusion criteria

  • Pregnancy
  • Current or prior diagnosis of neurologic, hypertensive, psychiatric, respiratory disorder, or anosmia/hyposmia
  • Some types of medication.
  • Olfactory sensitivity threshold (assessed via UPSIT® test kit (Sensonics International, Haddon Heights, NJ)

At enrollment, participants will complete a baseline survey on demographics, personality traits, and regular nature contact and perceptions. Study staff will also use the clinically-validated UPSIT® test kit (Sensonics International, Haddon Heights, NJ) to evaluate olfactory sensitivity and identify/exclude participants with undiagnosed smell loss.

Study staff will work with participants to schedule their forest bathing sessions and review instructions on how to prepare (e.g., by avoiding alcohol, marijuana, and certain foods, drinks, and household cleaning products with high terpene concentrations 24 hrs before their session).

Treatment and study plan

Forest bathing

Behavioral

Participants will be seated in a forest environment for an hour-long exposure to the forest

Primary outcomes

  1. Changes in the HF (ms^2) Component of HRV

    Time frame: At time point 2 (20 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).

    Assess whether VOC inhalation regulates psychophysiological outcomes of the terpenes-on vs. terpenes-off sessions.

    Ln High Frequency Heart Rate Variability at T2 (20 minutes into duration of exposure for each session)

  2. Baseline HF (ms^2) Component of HRV

    Time frame: At baseline (pre-exposure)

    Assess whether VOC inhalation regulates psychophysiological outcomes of the terpenes-on vs. terpenes-off sessions.

    Ln High Frequency Heart Rate Variability at baseline.

Secondary outcomes

  1. Blood Pressure (Diastolic in mmHg)

    Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).

    Assessed using mobile physiology equipment Diastolic blood pressure at T4 (60 minutes of exposure)

  2. Beats Per Minute (BPM)

    Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).

    Assessed using mobile physiology equipment BPM at time point 4 (60 minutes of exposure)

  3. Skin Conductance (μS)

    Time frame: At time point 2 (20 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).

    Assessed using mobile physiology equipment Skin conductance levels at time point 2 (20 minutes into exposure)

  4. Self-reported Positive Affect

    Time frame: At time point 2 (20 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).

    Assessed using the shortened Positive and Negative Affect Schedule (PANAS) Positive affect at time point 2 (20 minutes of exposure) Higher scale scores are indicative of better outcome Range 5-50

  5. Self-reported Stress

    Time frame: At time point 2 (20 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).

    Assessed using a single-item self report non-validated scale Self-reported stress at time point 2 (20 minutes of exposure) Higher scale score indicative of worse outcome Range 1-5

  6. Self-reported Negative Affect

    Time frame: At time point 2 (20 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).

    Assessed using the shortened Positive and Negative Affect Schedule (PANAS) Negative affect at time point 2 (20 minutes of exposure) Higher score on scale indicative of worse outcome Range 5-50

  7. Levels of CRP

    Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).

    Assessed using blood serum collected via standard clinical methods. CRP levels at time point 4 (60 minutes of exposure).

  8. Levels of Cortisol in Serum (ng/mL)

    Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).

    Assessed using blood serum collected via standard clinical methods Cortisol levels at time point 4 (60 minutes of exposure).

  9. Blood Pressure (Systolic in mmHg)

    Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).

    Assessed using mobile physiology equipment Systolic blood pressure at T4 (60 minutes of exposure)

  10. Level of TNF-alpha

    Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).

    Assessed using blood serum collected via standard clinical methods TNF-alpha levels at time point 4 (60 minutes of exposure).

  11. Levels of Il-6

    Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).

    Assessed using blood serum collected via standard clinical methods IL-6 levels at time point 4 (60 minutes of exposure).

  12. Baseline Blood Pressure (Diastolic in mmHg)

    Time frame: At baseline (pre-exposure).

    Assessed using mobile physiology equipment Diastolic blood pressure at baseline.

  13. Beats Per Minute (BPM)

    Time frame: At baseline (pre-exposure).

    Assessed using mobile physiology equipment BPM at baseline.

  14. Skin Conductance (μS)

    Time frame: At baseline (pre-exposure).

    Assessed using mobile physiology equipment Skin conductance levels at baseline.

  15. Self-reported Positive Affect

    Time frame: At baseline (pre-exposure).

    Assessed using the shortened Positive and Negative Affect Schedule (PANAS) Positive affect at baseline Higher scale scores are indicative of better outcome Range 5-50

  16. Self-reported Stress

    Time frame: At baseline (pre-exposure).

    Assessed using a single-item self report non-validated scale Self-reported stress at baseline Higher scale score indicative of worse outcome Range 1-5

  17. Self-reported Negative Affect

    Time frame: At baseline (pre-exposure).

    Assessed using the shortened Positive and Negative Affect Schedule (PANAS) Negative affect at baseline Higher score on scale indicative of worse outcome Range 5-50

  18. Levels of CRP

    Time frame: At baseline (pre-exposure).

    Assessed using blood serum collected via standard clinical methods. CRP levels at baseline

  19. Levels of Cortisol in Serum (ng/mL)

    Time frame: At baseline (pre-exposure).

    Assessed using blood serum collected via standard clinical methods Cortisol levels at baseline

  20. Blood Pressure (Systolic in mmHg)

    Time frame: At baseline (pre-exposure).

    Assessed using mobile physiology equipment Systolic blood pressure at baseline

  21. Level of TNF-alpha

    Time frame: At baseline (pre-exposure).

    Assessed using blood serum collected via standard clinical methods TNF-alpha levels at baseline

  22. Levels of Il-6

    Time frame: At baseline (pre-exposure).

    Assessed using blood serum collected via standard clinical methods IL-6 levels at baseline

Other outcomes

  1. Degree of Association of Sum Composite of Absorbed Dose of VOCs in Serum (μg/mL)

    Time frame: Time point 4 (60 min) for absorbed dose associations with same time point for DBP, SBP, Cortisol, Il-6, TNF-alpha, and CRP; and associations with Time point 2 (20 minutes) for HRV, SCL, positive affect, negative affect, self-reported stress, heart rate.

    Assess the association of absorbed dose (µg/mL) of forest-derived VOCs in serum with primary and secondary outcomes.

Sponsors and collaborators

Lead sponsor

University of Washington

Other

Collaborators

  • National Center for Complementary and Integrative Health (NCCIH)

Registry information

Important dates

Study start
2022
Primary completion
2023
Study completion
2023
First posted
Apr 7, 2022
Registry last updated
Sep 19, 2024

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.