Living close to plants lengthens human lifespan, according to a new study.

Researchers from the Harvard T.H. Chan School of Public Health and Brigham and Women's Hospital linked women who lived in homes surrounded by more vegetation to lower overall mortality rates in women.

The latest study revealed that women who lived in the greenest surroundings had a 12 percent lower overall mortality rate than those residing in areas with less vegetation.

"We were surprised to observe such strong associations between increased exposure to greenness and lower mortality rates," said Peter James, of the Harvard T.H. Chan School of Public Health's Department of Epidemiology, who co-authored the study. "We were even more surprised to find evidence that a large proportion of the benefit from high levels of vegetation seems to be connected with improved mental health."

Deeper analysis revealed that living in greener areas was also associated with better mental health, lower levels of depression, more opportunities for social engagement, higher physical activity and lower exposure to air pollution.

While this isn't the first study to link green environments to better health, it is the fist long-term study that included populations from all over the United States. The study used data from 108,630 women enrolled in the Nurses' Health Study across the U.S. from 2000 to 2008. Researchers viewed satellite images to calculate the level of vegetation surrounding homes. They also account for other mortality risk factors like age, socioeconomic status, ethnicity and lifestyle habits.

Analysis of combined study data revealed that the link between higher amounts of vegetation and lower mortality was strongest in women suffering from respiratory disease and cancer. Specifically, women residing in places with the most vegetation had a 34 percent lower rate of respiratory-disease related mortality and a 13 percent lower rate of cancer-related mortality compared to those residing in areas with the least vegetation.

"We know that planting vegetation can help the environment by reducing wastewater loads, sequestering carbon, and mitigating the effects of climate change," James concluded. "Our new findings suggest a potential co-benefit - improving health - that presents planners, landscape architects and policy makers with an actionable tool to grow healthier places."

The findings were published in the journal Environmental Health Perspectives.