Trail Running as a Therapeutic Modality: A Meta-Analytic Review of its Efficacy in

Trail Running as a Therapeutic Modality: A Meta-Analytic Review of its Efficacy in

Anxiety Management and Resilience Building

Owen R. Thornton

[email protected]

Abstract

The proposition that natural environments can confer significant mental health benefits is no

longer a fringe concept but a subject of extensive scientific inquiry. As global populations

become increasingly urbanized, the search for accessible, non-pharmacological interventions to

mitigate the rising prevalence of mental health disorders has intensified.1 This has led to the

formalization of concepts such as “green exercise,” which involves physical activity in the

presence of nature, and “ecotherapy,” which encompasses a range of structured therapeutic

interventions that utilize natural environments to promote healing.4 Trail running, the specific

focus of this report, exists at the intersection of these domains, representing a potent form of

green exercise that is increasingly being adopted not for competition, but for its perceived

therapeutic value. This section synthesizes the broad evidence base for nature-based health

interventions (NBHIs) to establish the scientific context from which the specific benefits of trail

running emerge. It will review the documented psychological and physiological effects, examine

the quantitative evidence from existing meta-analyses, and explore the theoretical frameworks

that explain these phenomena. Crucially, it will also address the methodological complexities and

limitations that characterize this field, providing a balanced and critical foundation for the

subsequent analysis.

1.1 The Scientific Basis of “Green Exercise” and Ecotherapy

The terms “green exercise,” “ecotherapy,” and “nature-based health interventions (NBHIs)”

describe a continuum of activities, ranging from incidental exposure to nature during physical

activity to highly structured, professionally guided therapeutic programs.2 At its core, this field

of study investigates the synergistic effect of combining physical activity with exposure to

natural environments.8 The body of research supporting the benefits of this synergy is substantial

and growing. A host of positive outcomes have been linked to nature exposure, including

improved attention, lower stress, enhanced mood, a reduced risk of psychiatric disorders, and

even increases in pro-social behaviors like empathy and cooperation.10 These interventions are

increasingly recognized as valuable, non-pharmacological adjuncts to conventional mental health

treatments, offering accessible, low-threshold, and sustainable strategies for managing mentalwell-being.1

The evidence points to a wide spectrum of both physiological and psychological effects.

Systematic reviews have demonstrated that engaging in green exercise can lead to significant and

measurable physiological changes. These include reductions in diastolic and systolic blood

pressure, resting heart rate, and levels of the stress hormone cortisol.5 Concurrently, the

psychological benefits are profound, with consistent findings showing reductions in symptoms of

anxiety, depression, anger, confusion, and fatigue.9 The combination of these effects underscores

the holistic impact of nature-based interventions, which simultaneously address the physiological

and psychological manifestations of stress and mental distress.

1.2 Meta-Analytic Evidence for Affective and Psychological Benefits

To move beyond qualitative descriptions and establish the magnitude of these effects, researchers

have employed meta-analysis to quantitatively synthesize the results of multiple studies. These

analyses provide a robust statistical foundation for the claims of green exercise’s mental health

benefits. A landmark multi-study meta-analysis, which aggregated data from 10 UK studies

involving 1,252 participants, found statistically significant overall effect sizes for improvements

in both self-esteem ($d = 0.46$, $p < 0.00001$) and mood ($d = 0.54$, $p < 0.00001$)

following acute bouts of green exercise.4 This provides strong quantitative evidence for a direct

and positive psychological impact.

The effect is particularly pronounced in the domain of negative affect. A separate meta-analysis

of 19 controlled trials with a combined 1,662 participants concluded that green exercise may

significantly lower a range of negative affective states, including anxiety, tension, anger,

depression, and fatigue.9 Another comprehensive review focusing specifically on urban green

exercise synthesized data to find a moderate and statistically significant positive impact on

mental health, with a standardized mean difference (SMD) of $-0.40$ ($95\%$ CI = $-0.56$ to

$-0.25$; $p < 0.001$).1 These findings are further corroborated by meta-analyses of NBHIs

targeted at individuals with diagnosed conditions, which have found large effect sizes for the

reduction of both anxiety and depression symptoms.2

However, a critical nuance appears when examining the impact on positive affect. While

negative affect is consistently and significantly reduced, the effect on overall positive affect has

not been found to be statistically significant in some large-scale meta-analyses.9 Despite this,

these same studies often report significant increases in specific positive emotions and states, such

as vigor, comfort, natural feeling, and relaxation.9 This suggests that the primary mechanism of

green exercise may be more strongly related to the alleviation of negative psychological states

than to the generation of overarching positive ones, a distinction that is crucial for a precise

understanding of its therapeutic action. The following table summarizes the key quantitative

findings from several prominent meta-analyses in the field.Table 1.1: Summary of Meta-Analytic Findings on the Psychological Effects of Green

Exercise

Study

(Source ID)

No. of

Studies

Total

Participants

Primary

Outcome(s)

Comparison Effect Size

(95% CI)

Key

Conclusion

Barton &

Pretty, 2010 4

10 1252 Self-Esteem,

Mood

Pre- vs.

Post-Interven

tion

Self-Esteem:

$d = 0.46$

($0.34,

0.59$) Mood:

$d = 0.54$

($0.38,

0.69$)

Green

exercise

leads to

significant

short-term

improvement

s in

self-esteem

and mood.

Weng &

Chiang, 2022

9

19 1662 Negative

Affect,

Positive

Emotions

Green vs.

Non-Green

Exercise

Not

specified, but

significant

References:

Previous Works

Owen R. Thornton, Sophia Ly, Isabella Colón et al. The Psychological Indicators of Success in Ultrarunning — A Review of the Current Psychological Predictors in Ultrarunning, 15 March 2023, PREPRINT (Version 1) available at Research Square [https://doi.org/10.21203/rs.3.rs-2675495/v1]

Owen R. Thornton, Wenjun Li, Hunter Cole, and Isabella Cólon. 2023. “Borderline Personality Disorder and Neuroplasticity: A Review”. International Neuropsychiatric Disease Journal 19 (2):1–8. https://doi.org/10.9734/indj/2023/v19i2367.

Ahtshamullah Chaudhry, Kimberly Morton Cuthrell, and Owen R Thornton. 2023. “Peptic Ulcer Disease; Stomach and Gastric Ulcers, a Concise Review”. International Research Journal of Gastroenterology and Hepatology 6 (1):30–39. https://journalirjgh.com/index.php/IRJGH/article/view/73.

Owen R. Thornton. 2023. “Effective Ultramarathon Pacing Strategies on Road and Trail: A Narrative Review”. Asian Journal of Advanced Research and Reports 17 (4):1–11. https://doi.org/10.9734/ajarr/2023/v17i4474.

Owen R. Thornton, Wenjun Li, Hunter Cole, and Isabella Cólon. 2023. “The Role of the Hippocampus in Borderline Personality Disorder: Structural and Functional Abnormalities”. International Neuropsychiatric Disease Journal 19 (2):28–38. https://doi.org/10.9734/indj/2023/v19i2370.

Owen R. Thornton. 2023. “Brain-Derived Neurotrophic Factor (BDNF) in Depression: A Mini Review of Clinical and Preclinical Evidence”. International Neuropsychiatric Disease Journal 20 (3):47–56. https://doi.org/10.9734/indj/2023/v20i3399.

Owen R. Thornton, Wenjun Li, Hunter Cole, and Isabella Cólon. 2023. “The Role of the Hippocampus in Borderline Personality Disorder: Structural and Functional Abnormalities”. International Neuropsychiatric Disease Journal 19 (2):28–38. https://doi.org/10.9734/indj/2023/v19i2370.

Owen R. Thornton, and Wenjun Li. 2024. “Global Trends and Correlations in Mental Health Disorders: A Comprehensive Analysis from 1990 to 2019”. International Neuropsychiatric Disease Journal 21 (2):36–53. https://doi.org/10.9734/indj/2024/v21i2425.

Owen R. Thornton. 2023. “Varying Levels of Carbohydrate and Fat Diets for Ultramarathon Running: A Review on Performance and Health Outcomes”. Asian Journal of Food Research and Nutrition 2 (3):93–103. https://journalajfrn.com/index.php/AJFRN/article/view/33.

Thornton, Owen R. The Role of Physical Activity On Brain-derived Neurotrophic Factors and Mental Health. 2025. https://doi.org/10.17615/xq7w-5t89

Thornton, O. R. (2025). The convergent frontier: Artificial intelligence in treatment planning for neural regeneration and tissue engineering in oral and maxillofacial surgery.

Thornton, O. R. (2025). What education could be: The AI method.

Thornton, O. R., & Li, W. (2025). Bulimia nervosa causing unknown threat to oral health: A comprehensive review. International Neuropsychiatric Disease Journal, 22(3), 166–174.

Thornton, O. R., & Li, W. (2025). The psychology and psychopathology of ultrarunning: Mental health and psychiatric insights into extreme endurance athletes. International Neuropsychiatric Disease Journal, 22(1), 1–5.

Thornton, O. R. (2024). Literature review: Recent advances in neuroscience. Medium.

Thornton, O. R. (2023). A current mini-review on the role of neuroplasticity in the treatment and management of borderline personality disorder.

Thornton, O. R. (2023). An overview of the role of neuroplasticity in the pathophysiology and treatment of mental illness: A mini-review.

Thornton, O. R. (2023). The role of neuroplasticity in the pathophysiology and treatment of mental illness: A comprehensive literature review.

Thornton, O. R. Sleep in elite ultrarunners: A look into athlete health.

11th