What Does the Research Say About Forest Therapy?
Forest therapy makes a quiet promise: spend slow, attentive time among trees, and your body will follow your attention into a calmer state. It is fair to ask whether science backs that up. The short answer: across hundreds of studies, time in forest environments is consistently associated with a shift toward a lower-stress physiological state — and the evidence is strongest exactly where most of us need it: stress and mood.
This article walks through the main findings the way we would want them explained to us: clearly, with named sources, and without overselling. Because this is a sensitive area, one thing first: forest therapy is not a medical treatment, and nothing here is medical advice.
Stress and the nervous system: the strongest signal
The foundational evidence comes from Japan. In field experiments across 24 forests with 280 participants, Park and colleagues (2010) measured lower cortisol, lower pulse, lower blood pressure, and greater parasympathetic nervous activity — the body's rest-and-recover mode — after forest walking and viewing, compared with matched time in city environments.
Larger syntheses point the same way. A meta-analysis by Qiu and colleagues (2022), pooling 21 blood-pressure studies with over 2,200 participants, found forest therapy significantly reduced blood pressure and salivary cortisol compared with urban controls — with sessions of twenty minutes or more outperforming shorter ones, and the largest effects in older participants and those who started with higher blood pressure. Notably, the cardiovascular and psychological benefits do not appear to be seasonal: studies in Hungary and Poland measured effects from winter forest walks too (Peterfalvi et al., 2021; Bielinis et al., 2018), which we look at closely in winter forest bathing. For what the two branches of the autonomic nervous system actually do, how much time the research points to, and where the cortisol evidence turns out to be weaker than the headlines, see nature and the nervous system.
Mood and mental wellbeing
A 2022 meta-analysis of randomized controlled trials — the most demanding study design — found that forest therapy significantly reduced symptoms of depression, even as its pooled effect on blood pressure across those particular RCTs did not reach significance (Yi, Seo & An, 2022). We mention both halves of that finding on purpose: honest science includes the parts that are still unclear. Reviews of the broader literature reach similar conclusions for stress, anxiety, and negative emotion, while noting that many studies are small and call for more rigorous, longer-term research (Stier-Jarmer et al., 2021; Hansen et al., 2017).
Burnout is the clearest case where the evidence stops short. The one randomized controlled trial to test a guided forest bathing walk directly against burnout found no change in burnout scores among physicians and healthcare professionals, even though the same participants reported feeling less stressed afterwards (Kavanaugh et al., 2022). We unpack that result, and what repeated sessions do differently, in forest therapy and burnout.
One intriguing thread concerns the forest air itself. An Italian observational study across 39 forest therapy sessions with 505 participants found that higher ambient concentrations of monoterpenes — aromatic compounds released by trees — were associated with greater reductions in anxiety (Donelli et al., 2023). The effect was small, about 1.3 points on a scale running from 20 to 80, and the design was observational rather than randomised. We give that study and the immune research their full context, limits included, in phytoncides: what forest air actually does.
Immunity, sleep, and the wider picture
The research program of Dr. Qing Li in Japan helped establish "forest medicine" as a field, reporting increased natural-killer-cell activity, lower stress hormones, and improved sleep after forest stays — with some effects appearing even in city parks (Li, 2018). The first meta-analysis of that immune evidence, published in 2024, pooled six studies with 79 participants between them and graded the certainty as low, largely because the studies could not separate the tree compounds from the walk (Fleming et al., 2024). Reviews also describe benefits for sleep quality and general wellbeing across varied groups, from office workers to older adults.
And the honest caveats: much of the evidence comes from Asian cohorts, samples are often small, and long-term randomized trials are still scarce. The field is real and growing — reviewers describe it as maturing rather than settled. That is exactly why we phrase things carefully: forest therapy may support your wellbeing; participants often report feeling calmer and more rested. Those phrasings are not marketing modesty. They are what the evidence currently supports.
What this means for a walk in a Slovenian forest
Taken together, the research sketches a practical recipe: regular, unhurried time in a forest, twenty minutes or more, attention resting in the senses. That is precisely what a guided session is designed to deliver — and in a country that is 58 percent forest, the "dose" is never far away. If you would like to experience it with a guide, see our guided experiences, or start with what forest therapy actually is.