Greening vacant urban land significantly reduces feelings of depression and improves overall mental health for the surrounding residents, a study has found.
The findings, published in the journal JAMA Network Open, have implications for cities across the US, where 15 per cent of land is deemed "vacant" and often blighted or filled with trash and overgrown vegetation.
The study found that people living within a quarter of a mile radius of greened lots had a 41.5 per cent decrease in feelings of depression compared to those who lived near the lots that had not been cleaned.
Those living near green lots also experienced a nearly 63 per cent decrease in self-reported poor mental health compared to those living near lots that received no intervention.
"Dilapidated and vacant spaces are factors that put residents at an increased risk of depression and stress, and may explain why socioeconomic disparities in mental illness persist," said Eugenia C South, an assistant professor at University of Pennsylvania in the US.
"What these new data show us is that making structural changes, like greening lots, has a positive impact on the health of those living in these neighbourhoods," said South.
For the trial, 541 vacant lots in Philadelphia were randomly assigned to one of three study arms: greening intervention, a trash clean-up intervention, or a control group with no intervention.
The greening intervention involved removing trash, grading the land, planting new grass and a small number of trees, installing a low wooden perimeter fence, and regular monthly maintenance.
Two sets of pre-intervention and post-intervention mental health surveys were performed among 342 people, 18 months before revitalisation and 18 months after.
Participants were asked to indicate how often they felt nervous, hopeless, restless, depressed, that everything was an effort, and worthless.
Results were most pronounced when looking only at neighbourhoods below the poverty line, with feelings of depression among residents who lived near green lots decreasing significantly - by more than 68 per cent.
Analyses of the trash clean-up intervention compared to no intervention showed no significant changes in self-reported mental health.
"The lack of change in these groups is likely because the trash clean-up lots had no additional green space created," said John MacDonald, a professor at University of Pennsylvania.
"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," said MacDonald.
The study shows transforming blighted neighbourhood environments into green space can improve the trajectory of the residents' mental health, the authors said.
Adding green space to neighbourhoods should be considered alongside individual treatments to address mental health problems in low resource communities.
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