Spring is finally here, and there is nothing like a walk in the park this time of year. But it turns out having plenty of greenery around is not only pleasant, it's also good for your health — and researchers at Harvard have the statistics to prove it.

Improving mental health by increasing the amount of greenery in one's environment is something researchers at Harvard's T.H. Chan School of Public Health have been investigating. Their latest research focuses on the effects that trees, shrubs and plants have on depression among teenagers. Carla Bezold lead the study, which involved some 9,000 adolescents.

"We had data on their depressive symptoms that they reported on a questionnaire," Bezold said, "and we had data on where they lived, which we used to determine how green the surrounding area was. And [we] saw that living in a greener neighborhood was associated with lower depressive symptoms."

The study found that young people living in the highest-quality green space were 11 percent less likely to be depressed than their peers with the poorest-quality green space.

Bezold says the positive effect of nature on our mental health has to do with countering the stress and distractions of urban life.

"The experience of nature, being around trees and other greenery, for example, provides a respite from that stress on our attention and cognition," she said. "So, that cognitive break, that cognitive restoration, is an opportunity for a boost in mental health."

That's something famed landscape architect Frederick Law Olmsted knew more than a century ago, according to his biographer Charles Beveridge, speaking in the documentary "Olmsted and America's Urban Parks." Olmsted designed the series of parks known as the "Emerald Necklace," which stretches between Boston and Brookline.

"He was, in fact, designing those spaces using all of his skill to create a place something that counteracted stress," Beveridge said. "[Olmsted] didn't use the term 'stress;' he was identifying a modern problem which was exacerbated by the fast moving fast growing cities of the 19th century."

Revere is one local community that's working to become a bit more "leafy." While touring the banks of the Pines River, Elle Baker of Revere's Healthy Community Initiatives Department proudly displays what the city has done and is planning. Through a state program known as "Greening the Gateway," 1,000 trees have already been planted along Revere's streets, with another 2,000 on the way.

The "Greening the Gateway" program is a state effort that funds tree planting in so-called gateway cities like Revere — former industrial centers now left with large blighted areas.

Along with the aggressive tree planting program, Baker said six playgrounds are in the process of being rebuilt; a half dozen parks are being spruced up; and Revere is getting ready to pave its part of an 11-mile bike and walking trail, which will stretch from Everett to Lynn, along the former Boston and Maine railroad right of way.

Of course, you could take a pill to reduce stress, but increasingly scientists are finding out you could also just take a walk in the woods.