Forest therapy is a guided practice of slowly and mindfully immersing yourself in a forest environment to improve physical and mental health. Originally called shinrin-yoku (literally “forest bathing”) in Japan, it was introduced in 1982 as a form of preventive health care by the Japanese Ministry of Agriculture, Forestry, and Fisheries. Drawing on ancient Shinto and Buddhist traditions that revered nature, it evolved into a structured activity that has since spread worldwide and attracted serious scientific attention.
It’s not hiking. It’s not exercise in the woods. Forest therapy is deliberately slow, sensory, and quiet. The goal is presence, not distance covered.
How a Session Works
A typical guided forest therapy walk lasts two to four hours, though the group might cover less than a mile in that time. A trained guide leads participants through a series of “invitations,” which are gentle prompts to engage the senses: noticing how light filters through the canopy, feeling the texture of bark, listening to layered birdsong, or simply sitting still and breathing. The Association of Nature and Forest Therapy, one of the leading certification bodies, describes this as “working in partnership with the forest,” with guides holding space rather than lecturing.
There are no strict rules about duration, activity type, or format. Sessions vary widely depending on the guide and the participants. Some are purely still (sitting or standing in one spot), while others involve slow walking. Many sessions end with a tea ceremony using foraged plants, creating a ritual of transition back to ordinary pace. You don’t need any equipment, fitness level, or prior experience.
What the Forest Does to Your Body
Trees release airborne compounds called phytoncides, antimicrobial oils that include substances like alpha-pinene and limonene. These compounds are measurable in forest air but nearly absent in city air. When you breathe them in over an extended period, they appear to trigger meaningful changes in your immune system.
Research led by Qing Li at Nippon Medical School found that phytoncides significantly increased the activity of natural killer (NK) cells, a type of white blood cell that identifies and destroys virus-infected and cancerous cells. Forest exposure boosted both the number of NK cells in the blood and the levels of anti-cancer proteins inside those cells. In female subjects, this immune boost lasted at least seven days after a single forest trip. Lab studies confirmed the mechanism: when NK cells were exposed to phytoncides for 48 to 144 hours, their cancer-killing activity increased in a dose-dependent manner.
The cardiovascular effects are equally concrete. A study comparing walking in a forest park versus an urban park found that forest walkers experienced a drop in systolic blood pressure of about 5 mmHg, a reduction in heart rate of roughly 2.5 beats per minute, and lower cardiac output, all signs that the heart was working under less strain. Artery flexibility also improved. Urban park walkers showed essentially no change in these measures.
Stress Hormones and the Relaxation Response
Cortisol, the body’s primary stress hormone, drops measurably during forest exposure. A systematic review and meta-analysis found that salivary cortisol levels were significantly lower in forest groups compared to urban groups, both before and after the intervention period. All but two of the included studies reported significant cortisol reductions in forest settings. The researchers noted that anticipated placebo effects (simply expecting to feel calmer in nature) likely play a role, but the physiological changes are real and consistent.
Heart rate variability, a key indicator of how well your nervous system can shift between stress and relaxation, tells the same story. A review of 625 subjects found that 79.2% experienced increased parasympathetic nervous system activity (the “rest and digest” mode) when exposed to a forest setting. Walking in a forest produced a 102% increase in parasympathetic activity compared to urban walking, and even passively viewing a forest scene produced a 56% increase. This shift was observed across all six studies that measured it.
Mental Health Effects
A meta-analysis published in Frontiers in Psychology examined forest therapy’s impact on mood using standardized psychological assessments. Forest therapy significantly reduced anxiety, anger, depression, fatigue, and confusion while boosting feelings of vitality and energy.
Duration matters, but less than you might think. Sessions as short as 15 minutes produced a measurable increase in vigor. Sessions between 15 and 60 minutes showed medium-sized reductions in anxiety and significant improvements in depression scores. Sessions of 60 minutes or longer produced the largest effects across every mood category, with particularly strong reductions in anxiety.
Both active and passive forms of forest therapy work. Walking through a forest (dynamic therapy) produced large reductions in anxiety, while simply sitting quietly in a forest (static therapy) significantly improved depression and energy levels. This is useful to know if mobility is a concern: you don’t have to be moving to benefit.
Forest Parks vs. Urban Green Spaces
City parks with trees are better than no greenery at all, but dense forest environments appear to offer something more. The study comparing forest and urban park walking found statistically significant differences in blood pressure, cardiac output, stroke volume, and arterial compliance, all favoring the forest. Urban park walkers saw minimal changes in cardiovascular function, while forest walkers showed consistent improvements.
The likely explanation comes back to phytoncides and the density of the canopy. A city park with scattered trees simply doesn’t produce the same concentration of volatile compounds as a closed-canopy forest. The sensory environment is also different: less noise, more complex natural soundscapes, more varied light patterns, and cooler temperatures under a full tree cover.
Forest Therapy in Health Systems
Several countries have begun integrating nature-based therapies into their health care systems through social prescribing, where doctors can refer patients to community activities rather than (or alongside) medication. In England, over 3,500 link workers are embedded in primary care as part of the NHS Long Term Plan, supporting more than 2.5 million referrals to community-based activities, including forest bathing and ecotherapy. Wales has a national framework for social prescribing that integrates with NHS Wales through regional partnership boards. Catalonia has built nature prescriptions into electronic health records, allowing doctors to refer patients directly. Portugal’s Social Prescribing Network is expanding the model to municipalities nationwide.
Forest therapy sits within the “green prescribing” category alongside ecotherapy and wilderness therapy sessions. It’s not positioned as a replacement for clinical treatment of serious mental illness or cardiovascular disease, but as a complementary intervention that addresses stress, mood, and overall resilience.
How to Start
You can practice forest therapy on your own or with a certified guide. If you’re going solo, the key principles are simple: go slow, put your phone away, engage all five senses deliberately, and stay for at least 20 minutes (though an hour or more will produce stronger effects). Choose the densest, most enclosed forest environment you can access. Walk without a destination. Pause often. Breathe deeply.
Guided sessions offer something harder to replicate alone: someone else managing the structure so you can fully let go of planning and agenda. Guides trained through organizations like the Association of Nature and Forest Therapy learn a specific sequence of sensory invitations designed to deepen your attention progressively. Many people find that having a guide helps them slow down in ways they can’t manage on their own, especially in the first few sessions.
The immune benefits observed in studies lasted about a week after a single forest trip, which suggests that monthly sessions could maintain elevated NK cell activity year-round. For stress and mood benefits, more frequent exposure appears better, though even a single session produces measurable changes. There are no established minimum doses, and no evidence of diminishing returns from going more often.