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Spend time in nature or green space

Regularly spending time in green space - a park, garden, woodland, or other natural setting - for its own sake rather than as a route to step counts or exercise targets.

At a glance

  • Evidence: Pooled cohort data link higher residential greenness to about 4% lower all-cause mortality per 0.1 NDVI increase.All-cause mortality · Moderate certainty · Observational association
  • What’s uncertain: Mortality studies measure residential greenness rather than time outdoors; they cannot establish an effect of taking nature breaks.
  • First step: Aim for repeated short exposures rather than one long outing; the pooled trials of nature-based activities that improved mood ran for 8 to 12 weeks with sessions of roughly 20 to 90 minutes.
  • Before you try it: Do not delay or replace treatment for significant depression or anxiety with time outdoors. All precautions
Read the full takeaway

Cohort evidence

The observational case is consistent and large: pooling nine cohorts covering more than 8 million people, each 0.1 increment in surrounding greenness went with about 4% lower all-cause mortality, and meta-analyses of nature-based activities find improvements in mood in controlled trials, while their pooled anxiety estimate is imprecise and the gardening subgroup pointed the other way.

Randomized evidence

The randomised evidence is where the entry has to be careful, because there is very little of it and it is not about individuals choosing a walk in the park: the strongest trial re-greened vacant lots in Philadelphia and measured the mental health of people living nearby. That trial found significant reductions in feeling depressed and worthless but a non-significant reduction in overall poor mental health, and a very large Australian cohort found no association between any green space measure and depression or anxiety, with grass cover actually associated with worse self-rated health.

Confounding and interpretation

Green space is also confounded by income, housing and self-selection in ways that are hard to remove. This is a reasonable habit with plausible mechanisms and a genuinely uncertain effect size for any one person, and it is a different claim from grounding or earthing, which is about skin contact with the earth and is not supported.

Wooden steps along a forest trail
Long-term healthStress & wellbeingVaries · Moderate · Free
Reviewed Sep 23, 2026
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Scientific evidence

What the research shows

Outcome assessments based on research, including its uncertainties and limitations.

All-cause mortality

Finding: Benefit supportedCertainty: Moderatestudies found a benefit from doing this

Evidence basis: observational studies (association, not proof of cause)

Pooled cohort data link higher residential greenness to about 4% lower all-cause mortality per 0.1 NDVI increase.

Population: Nine longitudinal cohort studies with 8,324,652 participants from seven countries in the pooled analysis; twelve studies with populations from 1,645 to over 43 million in the earlier review; studies included in a systematic review of urban green space; modelled population of Philadelphia adults in a health impact assessment.

Research details

Summary

A systematic review and meta-analysis of nine cohort studies covering 8,324,652 individuals from seven countries found that the pooled hazard ratio for all-cause mortality was 0.96 (95% CI 0.94-0.97) per increment of 0.1 NDVI within a buffer of 500 m or less of a participant's residence. Seven of the nine studies found a significant inverse relationship while two found no association, and heterogeneity was very high (I2 = 95%). An earlier systematic review of twelve studies in North America, Europe and Oceania, with populations ranging from 1,645 to more than 43 million individuals, found that most studies showed reduced cardiovascular mortality in greener areas but that evidence for all-cause mortality was more limited and no benefit was seen for lung cancer mortality. A systematic review of urban green space and health likewise found a consistent negative association with mortality, and a modelled health impact assessment estimated that 403 premature deaths (95% interval 298-618) could be prevented annually in Philadelphia if the city met its 30% tree canopy cover goal (Kondo 2020).

Why this certainty

This rests on very large, geographically diverse prospective cohorts with a consistent direction in seven of nine studies and a precise pooled estimate, which is why it is rated Moderate rather than Limited. It cannot be rated Strong because the evidence is entirely observational, the heterogeneity is extreme, the exposure is residential rather than behavioural, and confounding by socioeconomic position is not fully addressed in any of the retrieved sources.

Limitations

All of the pooled evidence is observational and exposure is residential greenness, not time actually spent outdoors, so it measures where people live rather than what they do. Heterogeneity is extreme (I2 = 95%), which means the pooled estimate averages over studies that disagree, and the exposure contrast (0.1 NDVI) is not something an individual can choose for themselves. Residual confounding by income, education, housing quality and neighbourhood selection is a serious concern in this literature, and the authors of the earlier review call for cohort studies with better covariate data and improved green space assessment. The health impact assessment is a modelled projection rather than an observed effect.

Effect estimate

Pooled HR 0.96 (95% CI 0.94-0.97) for all-cause mortality per 0.1 NDVI increase within 500 m

Sources for this outcome:

Mental health in relation to residential green space and structured nature-based activities

Finding: Mixed evidenceCertainty: Limitedstudies disagree, or the effect depends on who is studied

Evidence basis: randomised trials

Pooled trials of nature-based activities improved mood, but the anxiety estimate is imprecise, one gardening subgroup went the other way, and the largest cohort found no link with depression or anxiety.

Population: Meta-analysis of 50 studies including 16 randomised controlled trials in community-dwelling adults, some with pre-existing mental health problems; 442 community-dwelling adults in 110 vacant lot clusters in Philadelphia followed for 18 months; 46,786 city-dwelling Australian adults followed a mean of 6.2 years; 21 observational studies in children, adolescents and young adults; children and adolescents in additional systematic reviews.

Research details

Summary

A systematic review and meta-analysis of nature-based outdoor activities pooled 50 studies, of which 16 were randomised controlled trials with low to moderate risk of bias, and found improvements in depressive mood (-0.64, 95% CI -1.05 to -0.23), positive affect (0.95, 95% CI 0.59-1.31) and negative affect (-0.52, 95% CI -0.77 to -0.26), with the most effective interventions offered for 8 to 12 weeks and an optimal dose of 20 to 90 minutes. The pooled anxiety estimate was -0.94 as printed, but its published confidence interval (95% CI 0.94 to -0.01) is internally impossible and the pooled figure appears only in a figure, so the anxiety result should be treated as imprecise rather than as a demonstrated benefit. In the same analysis the two small gardening trials pointed the other way (SMD 0.43, 95% CI -0.02 to 0.89), so gardening should not be presented as uniformly best-evidenced. A cluster randomised trial of greening vacant urban land in Philadelphia found that living near greened lots was associated with a significant decrease in residents feeling depressed (-41.5%, 95% CI -63.6% to -5.9%) and worthless (-50.9%, 95% CI -74.7% to -4.7%), and a non-significant reduction in overall self-reported poor mental health (-62.8%, 95% CI -86.2% to 0.4%; P = .051). Observational syntheses point the same way: a systematic review of 21 studies in children and adolescents found a consistent beneficial association with emotional and behavioural difficulties, particularly hyperactivity and inattention, and limited evidence for mental wellbeing in children and depressive symptoms in adolescents. Against that, a cohort study of 46,786 Australian adults found no green space indicator associated with prevalent or incident depression or anxiety, and found that grass cover of 30% or more was associated with higher odds of incident fair to poor general health (OR 1.47, 95% CI 1.12-1.91) and prevalent psychological distress (OR 1.71, 95% CI 1.25-2.28), while a systematic review of urban green space reported mixed or null results for depression and stress measured via cortisol.

Why this certainty

There is randomised evidence, which distinguishes this from a purely observational claim, but it is a small number of trials in specific contexts - vacant lot greening and structured nature programmes - and the pooled effect sizes come with wide intervals in a literature where controlled studies carry moderate to high risk of bias. It is held at Limited rather than Moderate because the single largest and best-adjusted cohort found no association with depression or anxiety, and because one vegetation measure was associated with worse outcomes, which is hard to reconcile with a simple protective effect.

Limitations

The randomised evidence is mostly about changing the environment rather than an individual choosing to spend time in nature, so it does not directly test the habit as stated. The Philadelphia trial's primary overall mental health result did not reach significance (P = .051), its participants were not selected for mental health problems, and it measured proximity to greened land rather than use of it. Risk of bias was moderate to high in the controlled and uncontrolled studies in the meta-analysis, and the Australian cohort found no association with depression or anxiety at all, with one vegetation type associated with worse outcomes. A scoping review of 263 studies found that around 70% reported a positive association but that discordant definitions and measures make the evidence difficult to aggregate.

Effect estimate

Depressive mood -0.64 (95% CI -1.05 to -0.23) in meta-analysis of randomised controlled trials of nature-based activities

Sources for this outcome:

What people say

Who discusses this?

Public statements, with positions specific to each source and topic. These views do not determine the scientific evidence assessment.

What the research shows ↑

No sourced public statements added for this habit yet. This does not mean no one discusses it.

Practical steps and precautions

How to try it

  1. Aim for repeated short exposures rather than one long outing; the pooled trials of nature-based activities that improved mood ran for 8 to 12 weeks with sessions of roughly 20 to 90 minutes.
  2. Choose a setting you will actually return to within walking distance, because the observational evidence is largely about residential greenness and everyday exposure rather than occasional trips.
  3. Treat structured activities - green exercise, nature-based therapy, a walking group - as the best-evidenced format, since these were the intervention types behind the significant pooled mental health effects; the two small gardening trials in the same analysis increased anxiety rather than reducing it, so gardening is not the best-evidenced choice.
  4. Do not expect a change in depression or anxiety from green space alone. The largest cohort found no such association, and if symptoms are significant, green space is an addition to treatment, not a substitute.

Precautions

  • If you have significant depression or anxiety, do not delay or replace evidence-based treatment with time outdoors; no retrieved trial tested green space as a treatment for diagnosed depression against usual care.
  • People with hay fever, asthma or other pollen-triggered conditions should check local pollen forecasts and take usual precautions, since green space exposure is the exposure that provokes those symptoms.
  • Take standard sun and heat precautions, particularly in summer and at midday, and check for ticks after woodland or long-grass walks in areas where they are endemic.
  • Access is not equal: the health associations found in cohort studies partly reflect who lives near green space, so treat the size of the personal benefit as uncertain rather than as a guaranteed effect of any single walk.

References

Green spaces and mortality: a systematic review and meta-analysis of cohort studies.

Rojas-Rueda D, Nieuwenhuijsen MJ, Gascon M, Perez-Leon D, Mudu P · The Lancet. Planetary health · 2019

Systematic review and meta-analysis of cohort studiesVerified from full text
Open original source

Residential green spaces and mortality: A systematic review.

Gascon M, Triguero-Mas M, Martínez D, Dadvand P, Rojas-Rueda D, Plasència A, Nieuwenhuijsen MJ · Environment international · 2016

Systematic review with meta-analyses of observational studiesVerified from abstract
Open original source

Urban Green Space and Its Impact on Human Health.

Kondo MC, Fluehr JM, McKeon T, Branas CC · International journal of environmental research and public health · 2018

Systematic reviewVerified from full text
Open original source

Health impact assessment of Philadelphia's 2025 tree canopy cover goals.

Kondo MC, Mueller N, Locke DH, Roman LA, Rojas-Rueda D, Schinasi LH, Gascon M, Nieuwenhuijsen MJ · The Lancet. Planetary health · 2020

Modelled greenspace health impact assessment using published exposure-response functionsVerified from abstract
Open original source

Nature-based outdoor activities for mental and physical health: Systematic review and meta-analysis.

Coventry PA, Brown JE, Pervin J, Brabyn S, Pateman R, Breedvelt J, Gilbody S, Stancliffe R, McEachan R, White PL · SSM - population health · 2021

Systematic review and meta-analysis of controlled and uncontrolled studiesVerified from full text
Open original source

Effect of Greening Vacant Land on Mental Health of Community-Dwelling Adults: A Cluster Randomized Trial.

South EC, Hohl BC, Kondo MC, MacDonald JM, Branas CC · JAMA network open · 2018

Cluster randomized trialVerified from full text
Open original source

Impact of Green Space Exposure on Children's and Adolescents' Mental Health: A Systematic Review.

Vanaken GJ, Danckaerts M · International journal of environmental research and public health · 2018

Systematic review of observational studiesVerified from full text
Open original source

Association of Urban Green Space With Mental Health and General Health Among Adults in Australia.

Astell-Burt T, Feng X · JAMA network open · 2019

Prospective cohort studyVerified from full text
Open original source

A Scoping Review Mapping Research on Green Space and Associated Mental Health Benefits.

Wendelboe-Nelson C, Kelly S, Kennedy M, Cherrie JW · International journal of environmental research and public health · 2019

Scoping reviewVerified from full text
Open original source

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Editorial history and review method

Revision 3 · Approved for publication · Codex (publication approval explicitly authorized by site owner; category migration)

Prepared and checked with AI. Publication approval does not imply independent expert review. Request a correction.

Applied the audit corrections for nature-time. (1) The 403-premature-deaths estimate in the mortality outcome had no cited source; it is Kondo 2020 (doi 10.1016/s2542-5196(20)30058-9), a modelled health impact assessment rather than the Kondo 2018 review the entry cited, and it is now retrieved, stored as kondo-2020-tree-canopy-hia and cited from the outcome that uses it, with the summary saying explicitly that it is modelled. (2) The pooled anxiety estimate is no longer presented as a clean benefit: Coventry 2021's published interval (-0.94, 95% CI 0.94 to -0.01) is internally impossible, the pooled figure appears only in a figure and could not be recovered in corrected form, and the same analysis found the two small gardening trials increased anxiety (SMD 0.43, 95% CI -0.02 to 0.89). Both facts are now in the mental-health summary and the entry no longer recommends gardening as the best-evidenced format. (3) Deleted the unsourced claim that mediation analyses in this field have been criticised as suboptimally conducted and reported. (4) The mental-health outcome was labelled 'Benefit supported' for a habit the randomised studies do not test as stated, with the largest cohort in the same outcome null for depression and anxiety and one vegetation type associated with worse outcomes. The audit offered two options - rename the outcome to what was tested or record Mixed evidence - and both are applied: the outcome now reads 'Mental health in relation to residential green space and structured nature-based activities' and is labelled 'Mixed evidence'. Second reviewer must re-check: (a) whether the catalogue prefers Mixed evidence alone over Mixed evidence plus the rename; (b) whether the Coventry anxiety confidence interval can be corrected from the supplementary files, since no retrieved version of the paper carries the correct interval; (c) that no downstream copy turns the ER-style subgroup findings into a general claim that gardening reduces anxiety. Publication release 2026-10-04: site owner authorized a bounded AI audit and release of this exact revision. See docs/release-audit-2026-10-04.md for source-check findings and limits. No independent health-professional or peer review is claimed. Category migration 2026-10-04: removed the separate goals field; categories: Long-term health → Long-term health, Stress & wellbeing. Research assessments, sources, guidance, precautions, and evidence review dates are unchanged. This revision awaits publication approval; no new evidence review is claimed. Publication approval 2026-10-04: site owner explicitly accepted all current category-migration revisions for deployment and requested that remaining limitations be retained in docs/content-review-backlog.md. Approval applies to this exact content revision. No new evidence review, independent expert review, or clinical validation is claimed; existing precautions and disclosures remain in effect.