Can forest bathing significantly reduce stress hormones?

How much does forest bathing actually lower cortisol?

The drop in cortisol, the body's main stress hormone, is both consistent and measurable. A 2019 meta-analysis of 8 studies found that people who did forest bathing had salivary cortisol levels that were, on average, 0.08 μg/dL lower than those who spent time in an urban setting [5]. To put that in perspective, the typical morning cortisol range is about 0.1–0.8 μg/dL, so this is a meaningful shift toward a more relaxed state.

A more recent 2026 study in Brazil measured an even larger effect: after eight forest bathing sessions, participants' salivary cortisol dropped by 45%, from 0.29 μg/dL to 0.16 μg/dL [2]. That's nearly half the starting level. Another 2024 study found that just two days of forest immersion significantly lowered salivary cortisol (p < 0.05) in stressed volunteers [1]. So whether you look at a single session or a series, the hormone reduction is clear and clinically relevant.

Is forest bathing better than a walk in the city for stress hormones?

For cortisol specifically, forest bathing generally outperforms urban walking, but the picture is nuanced. The 2019 meta-analysis showed that forest groups had significantly lower cortisol than urban groups [5]. However, a 2025 study comparing a 30-minute walk in a forest versus a city found something surprising: cortisol actually dropped more after the urban walk (a decrease of 2.1 ng/mL) than after the forest walk (a non-significant drop of 0.5 ng/mL) [3]. This suggests that the physical activity itself—not just the environment—can lower cortisol, and that the effect may depend on the specific setting and duration.

That said, forest bathing offers other stress-reducing benefits that urban walking doesn't. The same 2025 study found that heart rate variability (a sign of relaxation) was significantly higher after the forest walk, meaning the body shifted into a more parasympathetic ('rest and digest') state [3]. Another study using brain imaging showed that a 2-hour forest session reduced activity in the prefrontal cortex during a stress test, while urban exposure did not [4]. So while cortisol drops may sometimes be similar, the overall stress-relief profile—including better mood, lower blood pressure, and improved nervous system balance—is stronger with forest bathing.

How quickly do the stress-hormone effects kick in?

The effects can be surprisingly fast. A 2022 study measured brain waves and found that even a 30-minute walk in a forest increased alpha waves (associated with relaxation) and boosted positive mood scores from 18 to 34 out of a possible 40 [6]. Another study showed that a single 2-hour forest bathing session significantly lowered salivary cortisol and heart rate in medical students preparing for exams [4]. So you don't need a week-long retreat—even a short, mindful walk in the woods can start reducing stress hormones within minutes to hours.

For longer-lasting changes, repeated sessions seem to build on each other. The Brazilian study that found a 45% cortisol drop used eight sessions over several weeks [2]. But the key takeaway is that the first session already produces a measurable effect, making forest bathing a practical, low-cost tool for acute stress relief.

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