A forest bath is a slow, intentional walk through a wooded area where the goal isn’t exercise or reaching a destination, but simply absorbing the forest through your senses. The Japanese Ministry of Agriculture, Forestry, and Fisheries coined the term “shinrin-yoku” in 1982, defining it as making contact with and taking in the atmosphere of the forest to improve mental and physical relaxation. Since then, a growing body of research has found that spending time among trees produces measurable changes in stress hormones, blood pressure, immune function, and mood.
How It Differs From a Hike
Hiking is about covering ground. Forest bathing is about slowing down enough to notice the texture of bark, the sound of wind moving through leaves, and the smell of damp soil. A typical session lasts anywhere from 15 minutes to a few hours, and you might only walk a short distance in that time. There’s no pace to keep, no summit to reach, and no fitness requirement.
Guided sessions often use what practitioners call “invitations,” simple prompts that direct your attention to one sense at a time. You might stand still with your eyes closed and notice where a breeze touches your skin, or look upward and follow the trunk of a tree to its canopy, then move your gaze from treetop to treetop. Another invitation asks you to breathe deeply through your nose and pay attention to where you feel the breath travel in your body. These aren’t meditation scripts so much as gentle redirections away from mental chatter and toward sensory experience. Over time, it becomes easier to settle into the slow pace, and people often find they can stay with a single sensory focus for longer stretches.
What It Does to Stress Hormones
Cortisol, the hormone your body releases under stress, drops during time spent in forests. In one study measuring salivary cortisol, walking in a forest environment decreased average cortisol levels from 9.70 to 8.37 nmol/L, while walking in an urban environment produced almost no change (10.28 to 10.01 nmol/L). About 69% of participants showed a measurable cortisol decrease after a forest walk. Levels of adrenaline, another stress-related hormone, also drop significantly in forest environments compared to urban ones.
Effects on Blood Pressure and Heart Rate
The blood pressure reductions documented across multiple studies are surprisingly consistent. In people with high or borderline-high blood pressure, forest walking lowered systolic pressure (the top number) by anywhere from 4% to 25% and diastolic pressure (the bottom number) by 2% to 30%, depending on the study and population. For context, a typical finding was a drop of about 8 to 16 mmHg in systolic pressure after a forest walking program.
Heart rate variability, a measure of how well your nervous system toggles between “active” and “rest” modes, also improves. One study found heart rate variability was 30% higher during forest viewing compared to an urban setting, a sign that the parasympathetic nervous system (the body’s “rest and digest” mode) becomes more active among trees.
Immune System Boost
One of the more striking findings involves natural killer cells, a type of white blood cell that identifies and destroys virus-infected cells and abnormal cells. After forest bathing trips, participants showed significantly higher natural killer cell activity and higher levels of the proteins these cells use to do their job. This wasn’t a short-lived spike. The boost in natural killer cell activity lasted more than 30 days after a single trip, which led researchers to suggest that one forest bathing trip per month could be enough to maintain elevated immune function.
The effect held in both men and women. In male subjects, elevated natural killer cell counts and activity persisted for at least 30 days. In female subjects, the increases lasted more than 7 days, confirming the same pattern.
Mental Health and Mood
When researchers measured mood before and after forest bathing using standardized psychological assessments, the pattern was clear: scores for depression, anxiety, anger, fatigue, and confusion all dropped, while feelings of vigor increased. Comparing forest bathing directly to urban walking, one study found vigor scores averaged 52.45 after forest bathing versus 45.85 after city walking, and fatigue scores were 42.55 after forest bathing versus 47.15 after urban walking. Forest bathing also improved sleep quality, particularly how refreshed participants felt upon waking.
These mood effects appeared in both men and women and across age groups, suggesting this isn’t a placebo response limited to people who are already enthusiastic about nature.
Why Forests Specifically
A reasonable question is whether any green space would produce the same results, or whether forests are special. The evidence points toward forests having an edge. A pilot study comparing walks in forest parks to walks in urban parks found that forest walkers had systolic blood pressure 5.22 mmHg lower, heart rates 2.46 beats per minute lower, and better arterial flexibility than those who walked in urban parks. Both groups were walking, so the exercise component was similar. The difference was the environment.
Trees release volatile organic compounds, sometimes called phytoncides, that you inhale as you walk beneath the canopy. These airborne chemicals are part of what gives forests their distinctive smell, and researchers believe they play a role in the immune and stress responses observed in studies. The combination of these compounds with reduced noise, filtered light, and the visual complexity of a forest canopy likely creates a sensory environment that’s qualitatively different from a manicured city park.
How to Try It
You don’t need a certified guide or a pristine wilderness. Find a wooded area where you can walk slowly without feeling rushed or unsafe. Leave your phone on silent or in your pocket. The core practice is simply to engage your senses one at a time: notice what you hear first, then what you smell, then what you see in your peripheral vision, then what the air feels like on your skin.
Sessions as short as 15 minutes produce some benefit, though longer immersions of one to two hours allow more time for your nervous system to shift gears. The immune benefits in the research came from multi-day trips, but the stress hormone and blood pressure changes showed up in single sessions. For maintaining the immune boost, the research suggests once a month is a reasonable frequency, though the ideal dose likely varies by person. If you live in an area without dense forest, a wooded park is a better option than no trees at all, even if the effects may be more modest than a full forest canopy provides.
The key distinction between forest bathing and simply “going for a walk in the woods” is intentional slowness. If you find yourself planning your evening or replaying a conversation, that’s normal. The invitations that guides use, like pausing to trace the outline of a single leaf or listening for the most distant sound you can detect, exist precisely to pull your attention back into sensory contact with the forest around you.