This page summarizes peer-reviewed research relevant to nature and forest therapy practice. Evidence in this field spans environmental psychology, psychoneuroimmunology, cardiovascular physiology, epidemiology, and public health. While long-term randomized trials are still developing, converging findings across experimental, clinical, and population-level research suggest that intentional time in forest and green environments is associated with measurable psychological and physiological changes.

Psychological Well-Being

Controlled trials and meta-analyses consistently show reductions in depression, anxiety, stress, and negative affect following structured forest bathing (Shinrin-yoku) interventions.

A 2023 meta-analysis of 36 studies (n = 3,554) found significant reductions in depression and anxiety, with psychological effects stronger than physiological changes (Siah et al., 2023). A systematic review of randomized controlled trials reported similar reductions in stress and anxiety following forest therapy programs (Kotera et al., 2020). Broader greenspace research also links nature exposure with improvements in mood, perceived stress, and self-esteem (Twohig-Bennett & Jones, 2018).

Experimental neuroimaging research has shown that walking in natural environments reduces rumination and decreases activity in the subgenual prefrontal cortex, a brain region associated with depression (Bratman et al., 2015).

Stress Physiology and Autonomic Regulation

Field experiments across multiple forest sites have demonstrated reductions in salivary cortisol, decreased sympathetic nervous system activation, and increased parasympathetic (rest-and-digest) activity following forest exposure (Park et al., 2010; Song et al., 2016).

A meta-analysis examining Shinrin-yoku interventions found reductions in systolic and diastolic blood pressure and heart rate, particularly among individuals with elevated baseline blood pressure (Ideno et al., 2017).

Together, these findings suggest that forest exposure influences stress regulation through autonomic nervous system pathways.

Immune Function

Multi-day forest exposure studies have demonstrated increases in natural killer (NK) cell activity and intracellular anti-cancer proteins, with some immune effects persisting for 7–30 days (Li et al., 2008; Li, 2010). Reviews have explored possible immune-modulating pathways associated with forest environments (Chae et al., 2021).

Volatile organic compounds emitted by trees (phytoncides) are one proposed mechanism, though causal pathways remain under investigation and larger replication studies are needed.

Green Space and Population Mental Health

Large-scale epidemiological research links green space exposure with lower incidence of psychiatric disorders.

A Danish longitudinal study of over 900,000 individuals found that childhood exposure to green space was associated with up to 55% lower risk of developing certain psychiatric disorders later in life (Engemann et al., 2019). Meta-analytic evidence similarly associates greater greenspace exposure with lower risk of depression and anxiety (Twohig-Bennett & Jones, 2018; Browning et al., 2023). Urban tree canopy density has also been correlated with reduced antidepressant prescription rates (Helbich et al., 2018).

While observational, the consistency of findings across national datasets strengthens inference.

Youth, Families, and Structured Nature Programs

Nature-based interventions show measurable benefits for youth and families.

A randomized controlled trial of a supported park prescription program found reductions in stress and loneliness among low-income parents over three months (Razani et al., 2018). A 15-week nature-based education intervention involving 362 youth demonstrated improvements in emotional, physical, social, and school functioning compared to controls (Sprague et al., 2021). Additional research suggests that green outdoor settings may improve attentional functioning in children with ADHD compared to built environments (Kuo & Taylor, 2004).

Green Prescribing in Healthcare Systems

Several countries, including the United Kingdom and New Zealand, have integrated green prescribing into primary care frameworks. In these systems, clinicians refer patients to structured time in nature as part of preventive or adjunctive care.

In the United States, park prescription programs are expanding but remain inconsistently funded and unevenly integrated into healthcare systems. Continued longitudinal research, program standardization, and policy support are needed to responsibly scale green prescribing.

Equity and Accessibility

Access to safe, high-quality green space is not evenly distributed.

Research shows that low-income communities and communities of color often experience reduced access to high-quality green environments due to patterns shaped by redlining, urban disinvestment, and environmental inequities (Rigolon, 2016; Nesbitt et al., 2019).

Environmental justice scholarship identifies green space access as a social determinant of health. Meaningful access requires attention to transportation, safety, cultural relevance, disability access, and financial barriers.

Guided forest therapy, when thoughtfully implemented, may serve as one model for increasing structured, supported access to restorative outdoor environments.

Limitations of Practice

Forest therapy is not a replacement for medical or psychological treatment. It is an evidence-informed practice that may complement broader health and wellness approaches.

Short-term benefits are supported across multiple study designs; however, continued longitudinal research is needed to clarify dose-response relationships, population differences, and long-term outcomes.

References

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, 112(28), 8567–8572. https://doi.org/10.1073/pnas.1510459112

Browning, M. H. E. M., Rigolon, A., McAnirlin, O., & Yoon, H. (2023). Where greenspace matters most: Associations between urban tree canopy and antidepressant prescriptions. Environmental Research, 216, 114552. https://doi.org/10.1016/j.envres.2022.114552

Chae, Y., et al. (2021). The effects of forest therapy on immune function: A systematic review. International Journal of Environmental Research and Public Health, 18(4), 1770. https://doi.org/10.3390/ijerph18041770

Engemann, K., Pedersen, C. B., Arge, L., Tsirogiannis, C., Mortensen, P. B., & Svenning, J.-C. (2019). Residential green space in childhood is associated with lower risk of psychiatric disorders from adolescence into adulthood. Proceedings of the National Academy of Sciences, 116(11), 5188–5193. https://doi.org/10.1073/pnas.1807504116

Helbich, M., de Beurs, D., Kwan, M.-P., O’Connor, R. C., & Groenewegen, P. P. (2018). Natural environments and suicide mortality in the Netherlands. Environment International, 113, 183–187. https://doi.org/10.1016/j.envint.2018.02.011

Ideno, Y., Hayashi, K., Abe, Y., Ueda, K., Iso, H., Noda, M., ... & Nakayama, T. (2017). Blood pressure-lowering effect of Shinrin-yoku (forest bathing): A systematic review and meta-analysis. BMC Complementary and Alternative Medicine, 17, 409. https://doi.org/10.1186/s12906-017-1902-3

Kotera, Y., Richardson, M., & Sheffield, D. (2020). Effects of Shinrin-Yoku (forest bathing) and nature therapy on mental health: A systematic review and meta-analysis. International Journal of Mental Health and Addiction, 20, 337–361. https://doi.org/10.1007/s11469-020-00363-4

Kuo, F. E., & Taylor, A. F. (2004). A potential natural treatment for attention-deficit/hyperactivity disorder: Evidence from a national study. American Journal of Public Health, 94(9), 1580–1586. https://doi.org/10.2105/AJPH.94.9.1580

Li, Q. (2010). Effect of forest bathing trips on human immune function. Environmental Health and Preventive Medicine, 15, 9–17. https://doi.org/10.1007/s12199-008-0068-3

Li, Q., Morimoto, K., Nakadai, A., et al. (2008). Visiting a forest, but not a city, increases human natural killer activity and expression of anti-cancer proteins. International Journal of Immunopathology and Pharmacology, 21(1), 117–127.

Nesbitt, L., Meitner, M. J., Girling, C., Sheppard, S. R. J., & Lu, Y. (2019). Who has access to urban vegetation? A spatial analysis of distributional green equity. Landscape and Urban Planning, 181, 51–79. https://doi.org/10.1016/j.landurbplan.2018.09.010

Park, B.-J., Tsunetsugu, Y., Kasetani, T., et al. (2010). The physiological effects of Shinrin-yoku: Evidence from field experiments in 24 forests. Environmental Health and Preventive Medicine, 15, 18–26. https://doi.org/10.1007/s12199-009-0086-9

Razani, N., Kohn, M. A., Wells, N. M., et al. (2018). Effect of park prescriptions on stress and well-being in low-income parents: A randomized controlled trial. PLOS ONE, 13(2), e0192921. https://doi.org/10.1371/journal.pone.0192921

Rigolon, A. (2016). A complex landscape of inequity in access to urban parks. Landscape and Urban Planning, 153, 160–169. https://doi.org/10.1016/j.landurbplan.2016.05.017

Siah, K. T. H., et al. (2023). Effects of forest bathing on psychological well-being: A meta-analysis. International Journal of Mental Health Nursing. Advance online publication. https://doi.org/10.1111/inm.13182

Song, C., Ikei, H., & Miyazaki, Y. (2016). Physiological effects of nature therapy: A review of research in Japan. International Journal of Environmental Research and Public Health, 13(8), 781. https://doi.org/10.3390/ijerph13080781

Sprague, N. L., Boddy, K., & Oddy, W. H. (2021). Nature-based education and child well-being: A 15-week intervention study. Health & Place, 69, 102571. https://doi.org/10.1016/j.healthplace.2021.102571

Twohig-Bennett, C., & Jones, A. (2018). The health benefits of the great outdoors: A systematic review and meta-analysis of greenspace exposure and health outcomes. Environmental Research, 166, 628–637. https://doi.org/10.1016/j.envres.2018.06.030