Spending at least two hours a week in parks, woods or other green spaces is linked to noticeably better health and well-being, and it does not seem to matter whether that time comes in one long walk or several short ones. That is the finding of a study of 19,806 adults in England, published in Scientific Reports in June 2019 and led by Mathew P. White, an environmental psychologist then at the University of Exeter Medical School.
People who logged 120 minutes or more of nature contact in the previous week were substantially more likely to report good health and high psychological well-being than those who logged none. The benefit plateaued between 200 and 300 minutes a week, with no additional gain from spending longer.
Where the two-hour number came from
The researchers used data from the government-run Monitor of Engagement with the Natural Environment survey and compared self-reported health and well-being against the total time each adult had spent visiting natural settings in the past seven days. Compared with no nature contact, the odds ratio of reporting good health for the 120 to 179 minute group was 1.59, and the odds ratio of reporting high well-being was 1.23.
The threshold held across sexes, age groups, occupational and ethnic categories, and among people living in both wealthy and poorer neighborhoods. It also held for adults with long-term illnesses or disabilities.
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"It's well known that getting outdoors in nature can be good for people's health and wellbeing but until now we've not been able to say how much is enough," White said when the results were released.
Split sessions count, and city parks qualify
Nothing in the analysis favored a single long expedition over several shorter visits. Two 30-minute walks on a weekend plus a couple of lunchtime strolls in a nearby park added up the same as one two-hour hike. Most visits recorded in the survey happened within about two miles of home, meaning local urban greenspaces contributed to the effect.
"Two hours a week is hopefully a realistic target for many people, especially given that it can be spread over an entire week to get the benefit," White said.
What might be doing the work
Time outdoors is associated with a package of physiological and cognitive changes that plausibly explain the pattern. A review by the Yale School of the Environment summarizes evidence that nature exposure can lower blood pressure and stress hormone levels, reduce nervous system arousal, and support immune function.
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Attention research points in the same direction. Psychologists Rachel and Stephen Kaplan proposed decades ago that natural settings let people pay attention more broadly and with less effort, allowing the brain's directed-attention system to recover from the constant demands of city life. More recent work at institutions such as the University of Chicago has documented measurable gains in memory and attention after short bouts of nature exposure.
Nature time also tends to bring incidental physical activity, social contact and, near lakes, rivers or the coast, exposure to so-called blue spaces, which some studies associate with additional mental-health benefits.
An observational study, not a prescription
Two important caveats belong with the two-hour figure. The design was observational and cross-sectional, so it can show a strong association but cannot prove that nature time causes better health. It is possible, for example, that healthier people are simply more able to get outside in the first place.
The finding is also based on self-reported health and well-being rather than clinical measurements. Even so, the size of the sample and the consistency of the threshold across very different groups make it a useful, concrete target. Two hours a week, broken into whatever chunks fit your schedule, at a nearby park or riverbank, appears to be a sensible weekly minimum to aim for.
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Anyone considering major changes to their activity levels because of a chronic condition should discuss it with their doctor.
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