There's no doubt urban green spaces are more pleasing to the eye than trash-strewn vacant lots that have been sitting in various stages of neglect for who knows how long.

But can transforming scattered patches of urban blight into green spaces also help to alleviate the blues?

An ambitious new study conducted in Philadelphia — a city with no shortage of abandoned buildings and vacant lots, particularly in lower-income neighborhoods — finds that green space is just what the doctor ordered.

In fact, even the most modest green spaces can go a long way in lifting the spirits of those living in underserved urban areas. Acting as an antidote to urban decay, the act of transforming vacant lots into green patches can have a balm-like effect on communities. Perhaps most important, these blight-zapping, mood-improving transformations can be initiated for relatively little money.

Ultimately, the study suggests that cities needn't necessarily dole out millions for peacock-y urban parks that are lavished with media attention and lure tourists by the subway-full. Packed with amenities and landscaped to the hilt, expansive — and expensive — parks aren't a bad thing. They do, however, often fail to adequately serve the communities that need them the most. So when it comes to truly making a difference in the lives of dispirited city-dwellers, smaller, it would seem, is better — or, at the very least, more cost-effective.

Published in JAMA Open Network, the study isn't the first to draw a parallel between urban green spaces and improved mental health. But as Rachel Morello-Frosch, a professor in the department of environmental science, policy and management at the University of California, Berkeley, who was not involved in the research explains to NPR, this particularly study is "innovative" in that it's not strictly observational.

"To my knowledge, this is the first intervention to test — like you would in a drug trial — by randomly allocating a treatment to see what you see," she explains.

A large vacant lot in Philadelphia. A large vacant lot in Philadelphia, a city with thousands of forsaken parcels of land that could be spiffed up for under $2,000. (Photo: Mike Linksvayer/Flickr)

The healing power of 'green interventions'

Here's how the controlled randomized trial unfolded:

First, researchers randomly selected 541 overgrown vacant lots spread across Philadelphia. Eugenia South, an assistant professor of emergency medicine at the University of Pennsylvania's Perelman School of Medicine who co-authored the study, tells NPR that there are "probably over 4,000 of them" with most concentrated in poorer swaths of the City of Brotherly Love.

The team then further divided these blighted parcels into 110 clusters and, from there, interviewed 442 adult Philadelphians living within a quarter mile of these clusters. The participants were asked questions primarily pertaining to their mental health and overall wellbeing.

"We used a psychological distress scale that asked people how often they felt nervous, hopeless, depressed, restless, worthless and that everything was an effort," South explains to NPR.

Following the initial round of interviews, South and her colleagues divided the 110 clusters into three groups.

One group of 37 clusters received a complete "greening intervention." That is, with the invaluable help of Pennsylvania Horticultural Society and its Landcare Program, these lots were fully transformed. Trash and overgrown vegetation were hauled away while small trees, grass and other features including low-slung wooden fences were brought in and, in effect, these neighborhood eyesores were reborn as attractive green spaces. At another 36 clusters, trash was removed and the unsightly lots received some basic maintenance. They weren't, however, fully greened like the first group. The remaining 37 clusters acted as the control group — they were left untouched. (After the conclusion of the study, these lots were also cleaned and greened.)

Eighteen months later, the researchers re-interviewed 342 of the same subjects. They found that those living near the vacant lot clusters that had been fully transformed into green spaces experienced significant improvements in mood compared to residents living in the vicinity of vacant lots that just had trash removed or were left in their current state.

"The lack of change in these groups is likely because the trash clean-up lots had no additional green space created," study co-author John MacDonald, PhD, explains in a Penn Medicine media release. "The findings support that exposure to more natural environments can be part of restoring mental health, particularly for people living in stressful and chaotic urban environments."

Overall, feelings of depression decreased by nearly 42 percent amongst those living near the fully greened vacant lots compared to the other groups. Self-reported "poor mental health" dropped by a staggering 62.8 percent amongst those same Philadelphians. The shifts toward improved mental health and wellbeing were most marked in the poorest neighborhoods randomly selected for the study.

"The poorer neighborhoods are the most hard-hit, as far as the neighborhood environment being dilapidated and run down," South tells Time magazine. "Those people are potentially the people who have the biggest health impact from the neighborhood environment, so making changes to this environment could have the biggest impact on them."

Previous research helmed by South and colleagues has linked decreased crime rates to newly greened vacant lots. These findings play an obvious role in the latest study: when residents feel safer in their neighborhoods, they're also likely to be happier and less stressed out. The same goes for another study from South and Co. that explored the correlation between decreased heart rates and vacant lots filled with greenery and trees, not junked cars and garbage. It would seem that exposure to nature — even in quick bursts and unexpected places — has a calming, restorative effect.

"The green space in and of itself is important," South explains to Time. "There are several mechanisms through which that's proposed to happen, including increased social connections and recovery from mental fatigue and coping with general life stress. The fact that it's green space, and not, say, a parking lot, is important."

As for the wooden fences installed at lots that received a full green intervention, South notes that these played a particularly important role — and it's not one that involves keeping people out. "That fence kind of delineates the space as a space that is now being cared for — it's a space that people are paying attention to," she says.

Vacant lot, Brush Park, Detroit An abandoned lot ripe for the greening in Detroit's Brush Park neighborhood. (Photo: Stephen Harlan/Flickr)

A low-cost method of fighting depression

One of the greatest takeaways gleaned by South and her fellow researchers is how cheap it is to produce such dramatic results.

Transforming a typical vacant lot in Philadelphia cost in the ballpark of $1,600 per 1,000 square feet and roughly $180 annually to maintain. (These are baseline figures for a basic greening and doesn't include things like swing sets, benches, water features and jungle gyms. These are, in the end, small patches of green and not fully realized parks.) As the Philadelphia Inquirer notes, $70 billion is spent annually on treating depression, making it one of the most costly health conditions in the United States.

While beautifying pockets of urban blight in poorer urban neighborhoods is not — and never will be — a full remedy to fighting the blues, the study suggests that green space can be an effective and affordable tool when used in conjunction with other treatments and therapies such as medication. In low-income neighborhoods, these more conventional treatments can be harder to come by, making additional green space an even more attractive supplementary option.

Fairmount Park, Philadelphia Philadelphia's Fairmount Park is one of the country's largest urban green spaces. Research finds that small, simple green spaces carved out of vacant lots can also do a world of good. (Photo: Michael W Murphy/Flickr)

"This really is a relatively low-cost intervention compared to the amount of money that is spent on other health problems," South tells the Inquirer.

Writing for Fast Company, Kelsey Campbell-Dollaghan notes that flashy, big-budget urban parks like the High Line boast many of the same mood-improving benefits as greened-up vacant lots. (In my neck of the woods, a relaxed early evening stroll in lushly planted Brooklyn Bridge Park works wonders on my blood pressure. The same goes for lazy weekend afternoons spent sprawled under a tree on Governors Island, another local park.)

But in the end, it's the small, hyper-local urban green spaces — "inexpensive, ubiquitous and simple" as Campbell-Dollaghan describes them — that have the potential to pack the most potent punch. They should not be overlooked.

As for gentrification, South acknowledges to the Inquirer the validity of concerns about the impact cleaned-up vacant lots could potentially have on real estate in some Philadelphia neighborhoods. As the general trend goes, once blight disappears, prices tend to shoot up and longtime and vulnerable residents are forced out.

South believes that communities should be involved with any changes large or small to avoid this.

"Our intention is not to push people out," she says. "We want it to be something that is helping the neighborhood be healthier for the people who live there."

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.