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7.23.2019

Greater Greenness in Communities Could Help Treat or Prevent Depression in Older Adults

The greener the better. That’s the main message from new research by the University of Miami Miller School of Medicine that found South Florida residents 65 years and older who live on a block with more vegetation are less likely to experience depression.

Compared with blocks with the lowest one-third of greenness, people living on blocks with medium greenness were 36 percent less likely to have depression. Those living amid the highest greenness levels had 52 percent lower odds, the Miller School team found in a study published in The British Journal of Psychiatry.

When adjusted for health comorbidities and demographics, the associations were still highly statistically significant, with the odds of depression reduced by 8 percent and 16 percent for medium- and high-greenness neighborhoods compared with low-greenness neighborhoods.

How could living on a block with more trees and other vegetation lower chances of depression? “There are several possible mechanisms, including through increased physical activity and social contact. Perhaps the most immediate and direct effects of exposure to greenness are in attention restoration, improvements in mood and stress buffering,” said Tatiana Perrino, Psy.D., lead author of the study published online in advance of the August 2019 issue of the journal.

“Depression is a significant public health concern, especially among older adults,” said Dr. Perrino, a clinical psychologist in the Miller School Department of Public Health Sciences. “Encouraging access and exposure to nature and green spaces may form part of clinicians’ recommendations for patient self-care, along with other behavioral and social strategies that can protect against depression.”

Importantly, greenness is a modifiable risk factor, meaning that the number of trees and other vegetation in a neighborhood can be increased. Maria Nardi, director of Miami-Dade Parks, Recreation and Open Spaces, a co-author of the study, is working on increasing greenness.

“To date, the county has planted over 200,000 trees, as part of Million Trees Miami, with the intention to plant one million trees in total,” said Scott Brown, Ph.D., research associate professor of public health sciences and architecture, and project director of the UM Built Environment, Behavior, and Health Research Team at the Department of Public Health Sciences.

The tree planting initiative has “a focus on lower-income neighborhoods, which tend to have less greenery than higher-income neighborhoods,” Dr. Brown said.

Evidence shows that greenness cover has its greatest impact on depression and other health issues among people living in low socioeconomic areas. “It is important to note that greenness had its greatest impact among the poor, which is not surprising because the poor are more bound by their immediate neighborhoods,” said study coauthor José Szapocznik, Ph.D., professor of public health sciences, architecture, psychology, and educational and psychological studies at the Miller School.

“It is not surprising that it affects across income levels like other environmental public health factors” such as polluted air, contaminated water, lack of access to health care and medications, and more, he said.

To conduct the study, the Miller School research team compiled data from three very different sources: satellite imagery, Medicare claims and the U.S. Census. The satellite photos allowed them to classify residential blocks in Miami-Dade County as low, medium or high vegetation. The Medicare data for 249,405 beneficiaries revealed that 9 percent had depression. The U.S. Census block data helped them put it all together by residence, and they included residents who did not move during 2010 and 2011.

The current findings add to other research by the Miller School research team that found neighborhood greenness has a positive relationship with health outcomes and well-being. For example, in previous studies they linked increased greenness to lower risks for heart disease and Alzheimer’s disease.

Dr. Perrino acknowledged that it can be difficult to change some patients’ health behaviors to improve mental or physical health. However, “exposure to greenness is typically something that is low in cost and effort, and something that can easily be combined with other activities of daily living such as going to the store, visiting neighbors or walking a pet.”

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