​Author: Nélida Quintero, PhD

​I recently had the opportunity to moderate a panel entitled: The 15-Minute City: Cities of the Future, that focused on the 15-Minute City approach to designing more livable and sustainable cities, at the New York Build Expo 2025, an architecture and construction event held in New York City. The panel was composed of architects and urban designers and included Theodore Liebman from Perkins Eastman, David Green from Arup, Patrick McCaffrey from Dattner Architects, and Rob Piatkowski from WSP. 

What is the 15-minute city model and what are its benefits and challenges?  
 
The 15-Minute City concept proposes that everything a person needs in daily life—work, education, healthcare, shopping, and recreation—should be accessible within a 15-minute walk or bike ride or public transportation trip from home.  The model is meant to foster stronger local communities, reduce reliance on cars, and improve overall well-being and quality of life. 

The term “15-Minute City” was popularized and advocated by urbanist and professor Carlos Moreno in the 2010s but its roots lie in older urbanist ideals revolving around human-scale, walkable cities and mixed-used development.  The concept gained global recognition during the COVID-19 pandemic, when lockdowns and travel restrictions challenged our understanding of proximity, mobility, and the importance of local neighborhoods. In 2020, Paris Mayor Anne Hidalgo embraced it as a central part of the city’s post-pandemic recovery plan. Since then, cities like Melbourne, Milan, Portland, and Bogotá have applied some of its principles as well.

While emphasizing proximity to basic resources, the model also underlines the importance of urban green spaces, community cohesion, and participatory planning. Though branded as innovative, the 15-minute city concept echoes ideas from a long lineage of urban thinkers and planners, such as Ebenezer Howard’s Garden City, which aimed to merge the best of urban and rural life through self-contained communities with green belts and easy access to jobs, emphasizing decentralization, walkability, and access to nature. In the 1980’s and 1990’s, the New Urbanist movement also called for walkable neighborhoods and mixed-used development, as a reaction against car-dependent suburban sprawl.  Around the same time, the concept of Transit-Orient Development (TOD) was also introduced, focusing on high-density and mixed-used development communities centered around public transportation. 

These models reflect a shared critique of 20th-century car-centric planning and a desire to bring people, activities, and green public space closer together. What makes the 15-Minute City unique is its focus on time as its primary metric. What these models also share are elements that have been shown to promote and sustain urban well-being.  

By emphasizing shorter travel times to most basic resources and daily activities, the 15-Minute City addresses the documented stress linked to long commuting times. Increased social interaction and access to nature, potentially facilitated by walkable, mixed-used neighborhoods with more public spaces, parks and third places, has also been shown to have multiple well-being benefits.  For instance, increased nature exposure may improve mood, reduce cortisol levels and increase cognitive performance. Walkable and bike-friendly areas may increase opportunities to strengthen weak social ties as well as encourage physical activity, which may reduce the risk of depression, anxiety and cognitive decline.
 
Challenges in Implementing the 15-Minute City
 
Some of the challenges for the implementation of the 15-Minute City, which were discussed by the New York Build Expo panelists, include the difficulty of retrofitting existing infrastructure, for example, in cities where city blocks are large or where urban zoning does not permit mixed-use or higher density development. There are also concerns and critiques regarding affordability, accessibility and equity around assuring that the benefits of the 15-Minute City are available to all.  

By 2050, +/-70% of the global population will live in a city, according to the United Nations’ projections.

Therefore, the United Nations’ Sustainable Goal 11 calls for cities that are inclusive, safe, resilient and sustainable, and urban design approaches such as the 15-minute city could help in working towards this goal.

​The 15-minute city stands as a hopeful model in which time, proximity, and connection take precedence over speed, distance, and isolation, in an effort to promote and sustain urban health and well-being, and enhance urban life  in the cities of the future. 

Interested in reading more?  Here are some suggested readings:
 
Gehl, J. (2011). Life between buildings. Island Press.
 
Kaplan, R., & Kaplan, S. (1989). The experience of nature: A psychological perspective. Cambridge university press.
 
Leyden K. M. (2003). Social capital and the built environment: the importance of walkable neighborhoods. American journal of public health, 93(9), 1546–1551.
 
Montgomery, C. (2013). Happy city: transforming our lives through urban design. Farrar, Straus and Giroux.
 
Moreno, C. (2024). The 15-Minute city: a solution to saving our time and our planet. John Wiley & Sons.
 
Moreno, C., Allam, Z., Chabaud, D., Gall, C., & Pratlong, F. (2021). Introducing the “15-Minute City”: Sustainability, resilience and place identity in future post-pandemic cities. Smart cities, 4(1), 93-111., 4(1), 93–100.
 
Roe, J., & McCay, L. (2021). Restorative cities: Urban design for mental health and wellbeing. Bloomsbury Publishing.
 
Whyte, W. H. (1980). The social life of small urban spaces. Conservation Foundation.
 
World Health Organization (WHO). (2018). Global action plan on physical activity 2018–2030: More active people for a healthier world. Geneva: World Health Organization.  Available at: https://www.who.int/publications/i/item/9789241514187

Speaking of Psychology: Designing cities to improve mental health, with Jenny Roe, PhD
​
On the Speaking of Psychology podcast by the American Psychological Association, environmental psychologist Dr. Jenny Roe shares how urban design can play a powerful role in shaping mental well-being, and why cities must be built with psychological health in mind.

Dr. Roe is a Fellow at the Centre for Urban Design and Mental Health and co-author of Restorative Cities, written alongside Centre founder Dr. Layla McKay. Her insights are rooted in evidence and advocacy, calling for a new kind of city: one designed to heal.

Here are a few takeaways worth reflecting on:

Nature isn’t a luxury, it’s a lifeline
Access to greenery, no matter how small, helps reduce stress, restore focus, and improve mental health outcomes. From city parks to street trees and rooftop gardens, the evidence is clear: nature heals.

The built environment can connect or isolate us
Thoughtfully designed public spaces, walk-able neighborhoods, and inclusive design help build trust, connection, and belonging, which are all key for resilient communities.

Equity in design is essential
The benefits of restorative urban design shouldn’t be reserved for the privileged. Dr. Roe advocates for inclusive planning that reaches all communities, especially those historically and systemically under-served.

Big changes aren’t always required
Even temporary or small-scale interventions, like pop-up parks or traffic-free zones, can make a measurable impact on mental health.

Cities like Paris and New York are showing what’s possible
From green corridors to car-free initiatives, cities around the world are beginning to prioritize mental well-being in their planning.
​
Dr. Roe’s message is simple but urgent: mental health should be a central goal of urban planning and design isn't just about aesthetics, it's about health, dignity, and human connection.​

APA Podcast Post:

• Speaking of Psychology: Designing cities to improve mental health, with Jenny Roe, PhD

About Jenny:

• Jenny Roe, PhD

Restorative Cities Book:

• Restorative Cities: Urban Design for Mental Health and Wellbeing (Bloomsbury, August 2021)

Published in the prestigious Journal of the American Medical Association last week at long last those of us interested in green space and mental health have a city-wide experimental study, and it’s good news! (South, Hohl, Kondo, MacDonald, & Branas, 2018)

KEY FINDINGS

• Creating urban green spaces reduced feelings of depression and worthlessness
• The effect was most pronounced in people with low income
• The effect did not involve active use of the green spaces
• The effect of simply tidying but not greening the spaces had minimal impact
• The effect was achieved with small-scale greening interventions

Until now, green spaces in one’s urban environment have been shown to confer a range of mental health benefits to their local populations only in observational epidemiological studies. In the most common type of these studies, snapshots of a populations’ access to green space and their mental health are measured at the same moment in time. These methodologies are of course hindered by problems for inferring causality.

The relationship between green spaces and mental health is a hugely complex one. There are a long list of ways in which the benefits are explained. The most well-evidenced mechanisms to date are: promoting exercise and socialisation, reducing exposure to air and noise pollution, reducing stress and restoring attention, and building senses of community and place attachment . These mechanisms, among many others, are hugely complex and very difficult to adjust for in observational studies despite best efforts. A common criticism which therefore arises from observational studies is whether the effect could be caused by any one of a thousand factors associated with green spaces, which could be good for mental health. Furthermore, the observational studies so far have reported widely variable results. Some have demonstrated impressive reductions in anxiety (de Vries et al., 2016) and depressive symptomatology (Triguero-Mas et al., 2015). While others have shown virtually zero impact at all (Houlden, Weich, & Jarvis, 2017). These variable results are likely in a large part due to the many confounding factors. In response, study after study, commentary after commentary, has been crying out for experimental style studies - natural experiments or randomized control trials (RCTs) – the benefits of which allow for the single issue of interest to be studied in isolation from the disruptive noise of the complex co-factors in the relationship. In RCTs of sound methodology we can be quite confident that the results we see are due to the factor we are interested in.

Step forward Eugenia South and her colleagues from the University of Pennsylvania and their RCT set in Philadelphia.
 
Green fingered Philly
 
Initially concerned with the high burden of mental health conditions, and in light of the then fledgling evidence for green space benefit, researchers extended their work which had previously shown reductions in crime rates following neighbourhood improvement projects to consider mental health outcomes (Kondo, Hohl, Han, & Branas, 2016). By early 2013 city officials in Philadelphia had identified nearly 45,000 lots of unused vacant, often derelict brownfield land across the city. Given such an opportunity authors designed their methodology to include three study arms into which randomly selected plots, grouped together into local clusters of a 0.25 mile radius, would be allocated. The first arm would be left as they were at present. The vacant plots in the second arm would be tidied up, and the third would be “greened”. The researchers would then be able to differentiate whether the “greenness” of the spruced-up space itself contributed anything to outcomes.

Random plots were selected from the master list, and random plots also from the list and within a 0.25 mile radius were included in the cluster. To be eligible for the study, lots were to be less than 5500sqft, deemed to be abandoned, and stricken with ‘blight’, for example that there was evidence of fly-tipping (dumping), abandoned cars, or numerous police reports concerning crimes associated with the lot. In total 110 clusters were formed, containing 541 lots. Over a period of two months gardeners from the Pennsylvania Horticultural Society transformed the third of these vacant plots allocated to the “greening” arm, and tidied the third in the second arm, they will continue to maintain these lots monthly for the foreseeable future.

Gardeners were instructed to follow a strict, replicable, modification process of grading the land, cleaning debris, planting grass and a small number of trees, and enclosing the space with a wooden fence with openings, in the aim of avoiding future dumping.
 
What impact on locals’ mental health?
 
In their study researchers randomly selected individuals living within the catchment areas of clusters and administered questionnaires before the intervention, and again after the intervention. There was a 77.4% success rate at interviewing the same people post-intervention at 18 months, achieving a final sample size of 342 subjects used in analysis. Questionnaires primarily consisted of key demographic information, financial status and a measure for mental health status. The short form “Kessler-6 scale” is a quick screening tool widely used for assessing poor mental health. Each question concerns a key symptom of psychological distress: nervousness, hopelessness, restlessness, depressive feelings, worthlessness, the feeling that everything is an effort, and a summary result which gives a good approximation of overall mental health and psychological distress. An annoying limitation of the short form Kessler scale is that we cannot make clinical judgments about the results: we can only identify the presence of depressive symptomatology, rather than making a diagnosis of clinical depression. However the two are of course highly related.

On to the results. Between individuals living in clusters which were greened versus those which were not, authors demonstrated significant reductions in two of the sub-categories of the K-6: depressive feelings were reduced by 41.5% and feelings of worthlessness by 50.9%(!) All other components had major drops in prevalence too. The combined figure showed impressive community wide reductions of psychological distress by 62.8% (95% CI, −86.2 to 0.4; P = 0.051). In the second arm of the study, tidying up the lots compared to no intervention produced weaker result than greening did, and while the prevalence of all psychological categories decreased, non came close to a real significance (a strong likelihood of true difference); overall psychological distress for example was reduced by 30.1% (95% CI, −74.7 to 93.2; P = 0.49).

Furthermore, and importantly, in line with other studies of green spaces in local communities and mental health outcomes (Roe, Aspinall, & Ward Thompson, 2016), evidence from this study suggests that these benefits are even more pronounced for those individuals with low incomes (in this study judged to be household income under $25,000 pa). Notably, feelings of depression dropped in this sub-group by 68.7%, (−86.5 to −27.5; P < 0.01). All other aspects dropped by large amounts, but with wide confidence intervals and without strong evidence of a true difference.

In short, authors, and readers, can conclude from this presented data, that the greening interventions conducted by these gardeners notably reduced the overall number of citizens with poor mental health, and has been especially good for reducing the number of people with depressed feelings, particularly for those with low incomes.

A call to arms for communities

The evidence presented by South and her colleagues marks an important point for green space / mental health research. For the first time, this is large scale, experimental data, which provides key, and long-needed reassurance that the work of observational studies to date is replicable when the complex web of confounding factors are evaporated away.

Furthermore this study offers much to the way in which to think about green space within urban design. Especially in conjunction with this team’s previous work on the reductions in crime rates in ‘greened’ neighbourhoods, this paper adds to the conversation about the mechanisms of action of the now-undeniable benefits of green neighbourhoods to the mental health of their residents. Recent emphasis in the debate had been placed on active use of green spaces, but this study may now shift thought back towards passive or indirect observable functions of green spaces (such as attention restoration, stress reduction and protection from nuisance environmental exposures), and promotes greenery as a key facet of improving the quality of neighbourhoods, given tidying the area alone produced only marginal benefit.

Next, we must ask environmental psychologists to consider why South’s interventions delivered improvement to rather specific facets of psychiatric symptomatology (depressive feelings and worthlessness specifically: the authors propose a renewed sense of local authorities caring about their communities as a possible explanation). Hence whether specific mechanisms of green space produce specific mental health symptom benefits? In this sense, facilitating other mechanisms with other flavours of green space interventions, perhaps larger green spaces for promoting recreation, and as community foci, other facets of psychiatric symptomatology will be addressed for an overall multifaceted tackling of community psychiatric burden.

Other important areas for consideration now should be the replication of these results across other cities, with larger sample sizes, and more rigorous, clinically validated assessments.

More than ever, we should feel renewed in a community focused approach to urban (re)design. That efforts in renewing small scale (and very small scale) blighted vacant lots in our communities (some clusters only renovating 5 lots to produce such improvements in mental health) is to be of benefit. It is highly likely that these small projects are achievable for many communities. Authors further report that these initiatives are  affordable too: in their previous work, greening improvements of this kind cost on average US$1,597, plus US$180 in yearly maintenance. Local government structures can now add “improving the mental health of my community” to the long list of reasons for revitalising derelict land that is perhaps too small and financially unappealing to property developers. Otherwise, in the spirit of work which has suggested community involvement and directorship of a community’s spaces is of multifaceted benefit through building a sense of community, of place, and of stewardship, councils might look to devolve authority of these small projects to community groups themselves. When all is said and done improving mental health is not the only outcome of improving the quality of local communities, but it is a major player in an interconnected web of community, environment and health, which the work presented here by South and colleagues could more reliably inform and encourage local and national decision makers to take a little more seriously.

de Vries, S., ten Have, M., van Dorsselaer, S., van Wezep, M., Hermans, T., & de Graaf, R. (2016). Local availability of green and blue space and prevalence of common mental disorders in the Netherlands. British Journal of Psychiatry Open, 2(6), 366-372. doi:10.1192/bjpo.bp.115.002469

Houlden, V., Weich, S., & Jarvis, S. (2017). A cross-sectional analysis of green space prevalence and mental wellbeing in England. BMC Public Health, 17(1), 460. doi:10.1186/s12889-017-4401-x

Kondo, M., Hohl, B., Han, S., & Branas, C. (2016). Effects of greening and community reuse of vacant lots on crime. Urban Stud, 53(15), 3279-3295. doi:10.1177/0042098015608058

Roe, J., Aspinall, P. A., & Ward Thompson, C. (2016). Understanding Relationships between Health, Ethnicity, Place and the Role of Urban Green Space in Deprived Urban Communities. Int J Environ Res Public Health, 13(7). doi:10.3390/ijerph13070681

South, E. C., Hohl, B. C., Kondo, M. C., MacDonald, J. M., & Branas, C. C. (2018). Effect of greening vacant land on mental health of community-dwelling adults: A cluster randomized trial. JAMA Network Open, 1(3), e180298. doi:10.1001/jamanetworkopen.2018.0298

Triguero-Mas, M., ., Dadvand, P., Cirach, M., Martínez, D., Medina, A., Mompart, A., . . . Nieuwenhuijsen, M. J. (2015). Natural outdoor environments and mental and physical health: Relationships and mechanisms. Environment International, 77, 35-41. doi:http://dx.doi.org/10.1016/j.envint.2015.01.012

Jacob King is a UD/MH Associate and junior doctor practising in UK. His main interest concerns the association between green space exposure and mental health, and how we can design interventions to promote this relationship.