Outdoor Therapies and the Baffling Burden of Proof
The question is not about evidence or credibility.
I’ve often wondered why outdoor therapies are so hard to engage institutions and funders with. Over the years, I have literally worked with hundreds of people - on courses, projects and through coaching - who have been trying to get outdoor ecotherapy programmes off the ground, only to be turned away. And I have been turned away myself, more times than I can remember. Back in the day, the excuse was often about lack of evidence, but that argument has now worn extremely thin, and this article aims to succinctly kill it off entirely.
There is now extensive, bio-medical and peer-reviewed evidence to support therapeutic outdoor practices. And it keeps growing.
The first wave
The first major wave of research established a remarkably consistent picture. Outdoor experiences reduce depression,[1,2,3] mental fatigue,[4] anxiety[5] and stress.[6,7,8] They improve mood [9] and cognitive function.[10,11] They reduce symptoms associated with trauma,[12] psychosis[13] and addiction.[14,15] They show promise with Attention Deficit Hyperactivity Disorder.[16] They slow cognitive decline,[17] increase longevity,[18] and improve quality of life for people living with Alzheimer’s and dementia.[19] They moderate the experience of pain.[20]
A significant pathway for many of these effects runs through immunity.[21] Outdoor approaches increase immune function in ways that appear to reduce risk across a striking range of conditions: cardiovascular disease, diabetes mellitus, cancer, upper respiratory infections, migraines, and more.[4,22,23] The breadth of this list is not incidental; it reflects the systemic, whole-body nature of what happens when we spend meaningful time outdoors.
Beyond the purely clinical, the evidence describes something more diffuse but no less significant. Improved sleep, increased energy, patience, creativity and motivation;[24,25] greater confidence and self-esteem; [26] an expanded sense of wellbeing and happiness;[27] and more pro-social behaviour. [28,29,30] These are not minor quality-of-life adjustments. They describe a fundamentally different way of being in the world.
The new wave
The new wave of literature reinforces all of this and sharpens it considerably.
A 2026 meta-analysis found that outdoor interventions significantly decrease tension, fatigue, confusion and negative affect, while increasing positive affect, vigour and sense of wellbeing.[31] These are not marginal effects. When physical activity undertaken in outdoor environments is compared directly to indoor exercise, it consistently produces superior mental health outcomes, alongside greater enjoyment and a stronger intention to repeat the experience.[32,33,34]
The physical health evidence is equally striking. A systematic review and meta-analysis of 143 studies found that outdoor exposure is associated with reduced cardiovascular risk, lower incidence of Type 2 diabetes, all-cause and cardiovascular mortality, improved metabolic markers, including decreased salivary cortisol, and better pregnancy outcomes, including reduced preterm birth.[35] For people already managing somatic or mental health conditions, structured outdoor activity produces improvements in quality of life, physical function and mental health outcomes.[36]
Now there is also good evidence on ‘dose’ - although this terminology feels compromising, as outdoor experiences are far more sophisticated than even the most advanced pharmacology. However, the research is still interesting. For example, data from nearly 20,000 people points to a threshold effect. 120 minutes outdoors per week is associated with significantly higher odds of good health and high well-being, with benefits peaking somewhere between 200 and 300 minutes weekly. Whether that time is accumulated in one go or across shorter visits makes no difference to the outcome.[37]
Neuroimaging is starting to contribute to the discourse about why time outdoors heals, too. Convergent findings across EEG, fMRI and structural MRI show that outdoor exposure produces acute reductions in stress-related brain circuit activity, shifts neural states toward patterns associated with attentional restoration, and is linked to long-term structural advantages in regions associated with cognition.[38] An 18-country study involving over 16,000 participants found that visits to landscapes, and inland- and coastal-water spaces were consistently associated with higher wellbeing and lower mental distress across diverse populations and seasons, and with lower likelihood of using antidepressant medication.[39]
One thing the evidence does not show is contraindications. The diverse and flexible nature of outdoor experiences, the fact that they can be undertaken in a dizzying array of forms, by almost anyone, makes this one of the most inclusive and cost-effective therapeutic approaches available. There are rare exceptions like photosensitivity and certain phobias. But as a general rule, time outdoors appears to be beneficial across a very wide range of human diversity, at a remarkably low per capita cost.
Beyond doubt
There are some gaps. [35,39,40] But the overall direction of the evidence is beyond doubt. The breadth, consistency and growing methodological rigour of the literature, from neuroimaging to large-scale epidemiology to meta-analysis, make a compelling case.
Outdoor approaches work; they work across a wide range of conditions and populations, and they carry negligible risk. The evidence is clear.
The question is not whether outdoor therapies are evidence-based and credible. It is why they remain peripheral to the mainstream health and education systems that claim to care about exactly the outcomes they reliably produce. Despite the evidence.
If you would like to learn more about professional outdoor ecotherapy practice, explore my upcoming online course.
References
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[2] Corazon, S., Nyed, P., Sidenius, U., Poulsen, D., & Stigsdotter, U. (2018). A Long-Term Follow-Up of the Efficacy of Nature-Based Therapy for Adults Suffering from Stress-Related Illnesses on Levels of Healthcare Consumption and Sick-Leave Absence: A Randomized Controlled Trial. International Journal of Environmental Research and Public Health, 15(1), 137.
[3] Park, B. J., Tsunetsugu, Y., Kasetani, T., Kagawa, T., & Miyazaki, Y. (2010). The physiological effects of Shinrin-yoku (taking in the forest atmosphere or forest bathing): Evidence from field experiments in 24 forests across Japan. Environmental Health and Preventative Medicine, 15, 18–26.
[4] Li, Q. (2009). Effect of forest bathing trips on human immune function. Environmental Health and Preventive Medicine, 15(1), 9–17.
[5] Bratman, G. N., Hamilton, J. P., Hahn, K. S., Daily, G. C., & Gross, J. J. (2015). Nature experience reduces rumination and subgenual prefrontal cortex activation. Proceedings of the National Academy of Sciences of the United States of America, 112(28), 8567–72.
[6] Tyrväinen, L., Ojala, A., Korpela, K., Lanki, T., Tsunetsugu, Y., & Kagawa, T. (2014). The influence of urban green environments on stress relief measures: A field experiment. Journal of Environmental Psychology, 38, 1–9.
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[8] Triguero-Mas, M., Donaire-Gonzalez, D., Seto, E., Valentin, A., Smith, G., Martínez, D., ... Nieuwenhuijsen, M. J. (2017). Natural outdoor environments and mental health: Stress as a possible mechanism. Journal of Environmental Research, 159, 629–638.
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[17] Harada, K., Lee, S., Park, H., Shimada, H., Makizako, H., Doi, T., Yoshida, D., Tsutsumimoto, K., Anan, Y., Uemura, K., & Suzuki, T. (2016). Going outdoors and cognitive function among community-dwelling older adults: Moderating role of physical function. Geriatrics and Gerontology International, 16(1).
[18] Fortes, C., Mastroeni, S., Sperati, A., Pacifici, R., Zuccaro, P., Forastiere, F., Agabiti, N., Piras, G., D’Amicis, A., & Ebrahim, S. (2013). Walking outdoors four times weekly for at least 15 minutes is associated with longevity in a cohort of very elderly people. Annals of Nutrition and Metabolism, 63(1).
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