A new study led by researchers at The University of Hong Kong (HKU) has established the first systematic weekly benchmarks for green space exposure and mental health. Drawing on 45 years of global research, the study reveals that even modest weekly contact with nature yields significant mental health benefits, with positive effects rising rapidly at lower levels of exposure before tapering off as visits become more frequent or prolonged.
The study, recently published in the prestigious international journal Environmental Psychology, was led by Professor Bin Jiang of the Urban Environments and Human Health (UEHH) Lab in the Faculty of Architecture at HKU. The interdisciplinary research team included Professor Peng Gong, HKU Vice-President and Pro-Vice-Chancellor (Academic Development); Professor Chris Webster, HKU Chair Professor of Urban Planning and Development Economics in the Department of Urban Planning and Design; and Professor Gunter Schumann of Fudan University, Charité Berlin, and the University of Cambridge. The first author is Dr Jiali Li, an HKU PhD graduate and senior member of the UEHH Lab.
Three levels of mental health benefits: How often and how long?
To address the practical question of how much time individuals should dedicate to nature, the research team analysed evidence published between 1980 and 2025. The meta-analysis focused on the frequency and cumulative duration of weekly green space visits, examining their impact on mental health outcomes such as stress, anxiety, depression, and mood.
The findings revealed a distinct non-linear relationship, which the researchers translated into three key reference points:
50% of the maximum estimated benefit: Achieved with just one visit or one hour of green space exposure per week.
90% of the maximum estimated benefit: Achieved with approximately four visits or four hours per week.
99% of the maximum estimated benefit: Achieved with approximately six visits or eight hours per week.
Highlighting the scientific significance of these thresholds, Professor Bin Jiang remarked, "The most striking aspect for me is the theoretical value of these findings, which suggest that the dose-response curves in most reviewed studies follow a remarkably consistent pattern. This indicates the potential existence of an objective scientific law. For public health, the findings suggest nature is not merely an object for aesthetic appreciation but a free, accessible 'medicine' for mental health, where the dosage matters."
Professor Chris Webster added, "It is surprising neither that nature exposure helps mental health nor that there is a dose-response curve. What was intriguing to find in this study was a consistent pattern across historical results, and the relatively small dose required to achieve measurable benefits."
The researchers clarify that these are rounded reference points derived from separate statistical models, rather than a combined schedule. The duration refers to cumulative time spent in green spaces across a week, not the length of a single visit. Furthermore, the percentages represent the proportion of the model's estimated maximum potential benefit rather than a direct percentage improvement in clinical symptoms.
The overarching trend indicates a law of diminishing returns: initial, manageable exposure provides the most substantial gains, whilst further visits or longer stays yield smaller incremental benefits. The findings describe broad relationships across studies and do not guarantee identical outcomes for every individual.
Refining the 'Dose-of-Nature' Framework
By mapping the dose-response curve and identifying the underlying theoretical mechanisms linking green space exposure to mental health, this study builds upon the team's pioneering research on 'greenness intensity' (the density of greenery encountered) published recently in Nature Cities.
Together, these studies significantly refine the Dose-of-Nature Framework, which evaluates green space exposure across four key dimensions: intensity (how much), frequency (how often), duration (how long), and accessibility (how easy to reach).
Commenting on the clinical and developmental potential of this framework, Professor Gunter Schumann said, "From a psychiatric perspective, the most relevant finding is that the steepest gains occur at low doses; one hour or one visit per week already achieves half of the modelled maximum response. This threshold is highly realistic for individuals experiencing low mood or reduced energy. Derived from a synthesis of observational studies, these benchmarks reflect population averages that complement rather than replace clinical treatment. Crucially, they offer an achievable starting point for clinicians and patients, while demonstrating that green space access is a modifiable determinant of mental health actionable through urban planning."
The new findings indicate that the health benefits associated with frequency and duration follow a different pattern to those of greenness intensity. The team noted that scientific evidence regarding accessibility remains limited, highlighting the need for future research into how green space quality, recreational activities, and personal circumstances influence health outcomes.
Practical implications for daily life and urban design
For the general public, the benchmarks offer an encouraging incentive to build simple habits into daily routines, such as taking a weekly walk in a park or choosing a greener route to work or campus. These reference points serve as a flexible guide that can be adapted to individual schedules and wellness needs.
For urban planners and landscape architects, the study underscores the importance of creating highly accessible, inviting green spaces. Features such as shaded seating, continuous pedestrian paths, and well-maintained vegetation are crucial to encouraging regular use. The researchers suggest that municipal evaluations of urban greening should focus not only on total vegetation coverage but also on how actively residents can and do engage with these spaces.
Reflecting on the study's practical mission, Dr Jiali Li explained, "We wanted to turn the broad advice from 'spend more time in nature' into something people can use in everyday life. Our findings suggest that even modest weekly contact with green spaces is associated with meaningful mental health benefits, while additional gains become smaller at higher levels of contact. My advice is to start with a routine you can sustain, such as a weekly park walk, and adjust it to your needs and circumstances. These benchmarks offer an achievable starting point, rather than a fixed prescription for everyone."
About the research team
Professor Bin Jiang is Director and Associate Professor of the Division of Landscape Architecture in the Department of Architecture, and Founding Director of the Urban Environments and Human Health Lab at the Faculty of Architecture, HKU. His research examines how urban environments and landscapes affect health and wellbeing, and how evidence can inform healthier cities. The study's authors are Dr Jiali Li, Professor Peng Gong, Professor Gunter Schumann, Professor Chris Webster and Professor Bin Jiang.
Research article
Li, J., Gong, P., Schumann, G., Webster, C., & Jiang, B.* (2026). A generalized relationship between dose of greenspace exposure behaviours and mental health responses. Journal of Environmental Psychology, 115, 103211. https://doi.org/10.1016/j.jenvp.2026.103211
