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Natural Medicine Journal

November 1, 2023

Prescription: Nature

A meta-analysis of nature Rx studies

Kurt Beil

ND, LAc, MPH
Yes
Impact of healthcare provider–based nature prescriptions on measures of cardiovascular health, psychological health, and physical activity.

This article is part of our February 2024 special issue. Download the full issue here.

Reference

Nguyen P-Y, Astell-Burt T, Rahimi-Ardabili H, Feng X. Effect of nature prescriptions on cardiometabolic and mental health, and physical activity: a systematic review. Lancet Planet Health. 2023;7(4):e313-328.

Study Objective

To synthesize evidence on the effectiveness of nature prescriptions and determine which factors are important for their success

Key Takeaway

Nature prescriptions (NRx) given by healthcare- and social-service providers have been shown to improve systolic and diastolic blood pressure and scores of depression and anxiety and to increase step-count and time spent engaging in moderate physical activity through regular involvement in local natural environmental settings. 

Design

Systematic review and meta-analysis 

Participants

From an initial search of 5 databases from 1999 to July 2021 (MEDLINE [Ovid], Embase [Ovid], PsycINFO [Ovid], CINAHL [EBSCO], and CENTRAL/CDSR [Cochrane]), investigators reviewed a total of 4,309 unique records and assessed 615 reports, of which 92 studies were included in the final systematic review and 28 were included in meta-analysis. The total number of participants was N=9,304, with a mean study size of n=102.

Studies were from a variety of countries, including South Korea (n=18; 20%), USA (n=16; 17%), Japan (n=10; 11%), UK (n=7; 8%), and China (n=5; 5%). A diverse range of ages, from children to elderly, and socioeconomic backgrounds was represented. The reasons for NRx included many different clinical diagnoses, with mental health (n=13; 14%), cardiovascular (n=12; 13%), and musculoskeletal (n=6; 7%) conditions being the most common.

Inclusion criteria were for controlled trials of nature-based interventions (NRx, see below) recommended by health or social providers that collected data on physical, psychological, cognitive, or behavioral health outcomes. Exclusion criteria included nonhuman participants, noncontrolled studies, simulated nature exposure (eg, video, virtual reality), specialized environments (eg, wilderness therapy), and school/after-school based activities. 

Interventions

The reviewed NRx studies used a variety of nature-based settings. The most common were forests and nature reserves (n=32; 35%), urban parks (n=26; 28%), or community/allotment, botanical, or personal gardens (n=25; 27%). NRx activities included walking in nature (n=42; 46%), individual or group sports (n=30; 33%), gardening (n=27; 29%), meditation/breathwork (n=25; 27%), arts and crafts (n=4; 4%), and just relaxing/enjoying the setting (n=2; 2%). Frequency and duration of exposures were highly variable between studies. 

Study Parameters Assessed

Data included in the meta-analysis were systolic blood pressure, diastolic blood pressure, depression (various scales), anxiety (various scales), daily step counts, and weekly time spent on moderate physical activity. 

Risk of bias was determined to be moderate to high, based on small study sizes, high study dropout/noncompletion rates without participant explanation, the inherently subjective nature of many of the psychometric scales used in the various studies, and (based on the intervention method) a lack of possible blind/double-blind study designs. 

Key Findings

NRx resulted in improvements in:

  • Systolic blood pressure (mean difference –4.82 mm Hg [–8.92 to –0.72], I²=60%);
  • Diastolic blood pressure (mean difference –3.82 mm Hg [–6.47 to –1.16], I²=59%);
  • Depression scores (postintervention standardized mean difference –0.50 [–0.84 to –0.16], I²=83%);
  • Depression change from baseline (standardized mean difference –0.42 [–0.82 to –0.03], I²=0%);
  • Anxiety scores (postintervention standardized mean difference –0.57 [–1.12 to –0.03], I²=91%); 
  • Anxiety change from baseline standardized mean difference –1.27 (–2.20 to –0.33);
  • Daily step counts greater than control conditions (mean difference 900 steps [790 to 1010]); and
  • Weekly time of moderate physical activity (mean difference 52.9 min [33.7 to 72.1]).

Transparency

Study funding was provided through the Australian National Health and Medical Research Council Boosting Dementia Research Leader Fellowship (1140317) and the National Health and Medical Research Council Career Development Fellowship (1148792). Authors declared “no competing interests” in the conduct or publication of this study.  

Practice Implications & Limitations

Exposure to the natural world is increasingly recognized as a mechanism for health promotion, disease prevention, and even disease treatment.1,2 Contact with nature has been shown to positively affect biomarkers of allostatic load (ie, heart rate, blood pressure, heart rate variability, and salivary cortisol);3 measures of brain activity (ie, electroencephalogram [EEG], functional magnetic resonance imaging [fMRI]);4 and mental well-being,5 vitality,6 and quality of life.7 Presence and use of natural “green spaces” is associated with lower rates of mortality,8 cardiovascular disease,9 type 2 diabetes,10 obesity,11 depression, and anxiety.12 The health benefits of natural spaces are truly holistic and extend beyond physical and mental/emotional benefits to include enhancement of social,13 spiritual,14 and even environmental health.15

This is especially pertinent in an era of simultaneous, epidemic levels of chronic disease, increasingly indoor and sedentary lifestyles, growing social isolation, and ecological destruction.16-18 Data support the theory of biologist EO Wilson’s “biophilia hypothesis”19 that human affinity for the natural world is an intrinsic adaptation resulting from millions of years of co-evolutionary exposure with our surrounding environments.20 The dearth of contact with the natural world in modern society has been suggested to contribute to a variety of chronic physical and mental/emotional conditions known colloquially as “nature deficit disorder.”21 Recent events like the global Covid-19 pandemic have demonstrated how essential contact with nature is and how opportunities to access local green spaces benefit individuals’ and community’s physical, mental, and social health.22,23

One recent method of promoting more time in nature is the use of formal nature prescriptions by physicians and other healthcare and social service providers.24 People have shown they are more likely to engage in a lifestyle or health-behavior change when given formal prescriptions.25,26 Use of nature Rx is increasingly common as providers understand the scientific validity of empirical studies identifying the health benefits of time in nature and recognize NRx as an accepted and available professional practice.

People have shown they are more likely to engage in a lifestyle or health-behavior change when given formal prescriptions.

These methods are being increasingly adopted in countries like the UK, where the National Health Service has begun a £5.77-million ($7.06-million) “green social prescribing” program to improve health outcomes and address health inequalities.27 In Japan, people commonly visit national “forest bathing centers” to engage in physician-personalized, nature-based mindfulness nature walks known as shinrin-yoku.28 In the United States, resources like Park Rx America are facilitating the writing and inclusion of NRx in patient EHR (electronic health record) charts.29

To increase adherence/compliance and optimize health outcomes of a NRx program, it is best to adopt a patient-centered approach, integrating experience and communication between various partners (ie, healthcare, recreation, social services, transportation, etc).30 An optimal NRx includes:

  • Patient choice of activity to reflect personal interests and cultivate self-efficacy;
  • Specific “dosage” of NRx, including activity, frequency, and duration;
  • Sharing information about specific health benefits for conditions being addressed;
  • Information about local resources (eg, parks), including location, proximity, amenities, hours, and contact info;
  • Opportunities for individual or group social experience; and
  • Clinical followup and opportunities for patient accountability, input, and feedback.

Incorporation of NRx in the clinical treatment plan can be a simple and effective method of improving multiple aspects of patient health and well-being. 

Limitations of the current study include the inherent moderate-to-high risk of bias (see above); the aggregation of meta-data preventing detection and/or recommendation of potential NRx benefits for specific demographic groups based on age, sex/gender, socioeconomic status, etc; and the relatively recent inclusion and study of NRx in healthcare results in high meta-analytic heterogenicities (I2). Standardization of clinical and research protocols will allow for more uniform and reliable collection of data and detection of health-related outcomes. 

Categorized Under

Kurt Beil

ND, LAc, MPH

Kurt Beil, ND, LAc, MPH, is a naturopathic physician and licensed acupuncturist and holds a master’s degree in public health focused on the benefits of green space as a sustainable public-health promotion tool. He did his postdoctoral work at the Helfgott Research Institute on biomarker and psychometric assessment of the restorative and therapeutic effects of natural vs built urban environments. Dr Beil has been an advisor to the Children & Nature Network’s “Nature Research Database” and was the founding cochair of the Nature & Health subcommittee of the Intertwine Alliance in Portland. He also moderates a Facebook group (“NDs for Nature”) for the naturopathic medicine community on the clinical health benefits of contact with nature. Dr Beil maintains a clinical naturopathic and Chinese medicine practice in Happy Valley, Oregon, focusing on chronic disease. He can be reached via email or www.drkurtbeil.com.

References

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