📚 Part of our Sleep & Stress Guide — an evidence-based guide.
The finding that time outdoors reduces stress sounds like the kind of soft advice that dissolves under scrutiny. It mostly does not — but the strength of the evidence varies a lot depending on which claim you are examining.
What is measured, not just reported
The useful studies do not rely only on people saying they feel better. Time in green space has been associated with lower salivary cortisol, reduced heart rate and blood pressure, increased heart rate variability — a marker of parasympathetic, or “rest and digest”, activity — and reduced activity in the subgenual prefrontal cortex, a brain region linked to rumination.
That last one comes from a well-known Stanford experiment: participants who walked 90 minutes in a natural setting showed reduced rumination and reduced activity in that region, while those walking the same duration beside a busy road did not.
How much and what kind
The most-cited figure comes from a large UK study: people reporting at least 120 minutes per week in nature were consistently more likely to report good health and wellbeing, with the benefit plateauing around 200–300 minutes. It did not matter whether that was one long visit or several short ones.
Important caveat: that study is cross-sectional. It cannot establish that nature caused the wellbeing rather than healthier people going outside more. It is the most quoted number in this field and the weakest kind of evidence.
Shorter exposures also show effects. Experiments have found measurable stress reduction from 20 to 30 minutes in a natural setting, and even from views of greenery through a window — the effect scales with immersion but does not require it.
Why it might work
Several mechanisms are proposed and none is fully settled.
Attention restoration. Nature engages attention effortlessly, allowing the directed-attention systems drained by work and screens to recover.
Stress reduction. Natural environments may trigger an innate parasympathetic shift.
Displacement. Time outdoors typically means movement, daylight and often social contact — each independently beneficial. Some of what looks like a nature effect may be a daylight and activity effect.
Air quality and noise. Lower pollution and less traffic noise, both linked to cardiovascular stress.
One popular claim deserves scepticism: that inhaling phytoncides — compounds released by trees — boosts immune natural killer cells. The studies behind it are small, mostly from one research group, and often lack adequate controls. Treat it as unproven.
Making it practical
Two hours a week is roughly 20 minutes a day, or a single weekend walk. It does not need to be wilderness — urban parks, tree-lined streets, gardens and waterfronts all appear in the research, and blue space such as rivers and coastline shows effects at least as strong as green.
Practical ways in: walk part of a commute through a park, take calls outside, eat lunch outdoors, exercise outdoors rather than indoors, and leave the phone in a pocket — rumination follows you if you bring the feed.
Access is not equal. Lower-income neighbourhoods have measurably less green space, which makes this partly a matter of urban policy rather than personal choice.
When to see a doctor
Time outdoors is a supplement to treatment, not a substitute for it. See a doctor if low mood, anxiety or loss of interest persist most days for two weeks or more, or if stress is affecting sleep, appetite or work (how chronic stress affects the body). Seek urgent help for thoughts of self-harm.
The honest bottom line
Nature exposure shows real, measurable effects on cortisol, heart rate variability and rumination. The famous 120-minutes-a-week figure comes from cross-sectional data and should be held loosely. Urban parks count, blue space works too, and the immune-boosting tree compound story is not well supported. The cost is zero and the downside is none, which is a good reason to do it regardless of how the evidence eventually settles.
Frequently asked questions
Does being in nature reduce stress?
Yes. Spending time in green space is consistently linked to lower stress, lower blood pressure, and improved mood, with measurable effects on the body's stress response.
How much time in nature do you need?
Even short doses help. A brief walk in a park or greenery can shift your stress response, and studies often find benefits from as little as 20-30 minutes.
What is forest bathing?
Forest bathing (shinrin-yoku) is the practice of slowly, mindfully spending time among trees. It's associated with reduced stress and improved well-being.