A quick walk in the park may just be the emotional pick-me-up you need.

The first study of its kind shows that those who visited an urban park use happier language and express less negativity on Twitter than before the visit. This boost in mood, the paper further reports, can last for up to four hours afterward.

Christmas come early

“We found that, yes, across all the tweets, people are happier in parks,” says Aaron Schwartz, a University of Vermont (UVM) graduate student who led the new research, “but the effect was stronger in large regional parks with extensive tree cover and vegetation.”

The effect is definitely strong — the team found that the increase in happiness people derived from visiting an area of urban nature was equivalent to the mood spikes seen on Christmas day (which they explain is by far the happiest day of the year on Twitter). Given that more and more of us live and work in the city — and given the growing rate of mood disorders we experience — the findings can help inform public health and urban planning strategies.

For the study, the team spent three months analyzing hundreds of tweets daily that were posted from 160 parks in San Francisco. Visitors showed the effects of elevated mood in their posts after visiting any one of these urban nature areas. Smaller neighborhood parks showed a more modest spike in positive mood, while mostly-paved civic plazas and squares showed the least mood elevation.

This suggests that it wasn’t merely going out of work, or being outside, that caused the boost in mood. The team says areas with more vegetation had the most pronounced impact, noting that one of the words that shows the biggest uptick in use in tweets from parks is “flowers.”

“In cities, big green spaces are very important for people’s sense of well-being,” says Schwartz.

“We’re seeing more and more evidence that it’s central to promoting mental health,” says Taylor Ricketts, a co-author on the new study and director of the Gund Institute for Environment at UVM.

The study’s findings are important as they quantify the benefits of natural areas beyond immediate monetary gains (i.e. “how many dollars of flood damage did we avoid by restoring a wetland?”) and look at its direct effects on public health.

The team used an online instrument called a hedonometer — invented by a team of scientists at UVM and The MITRE Corporation — to gather and analyze the tweets. The instrument uses a body of about 10,000 common words that have been scored by a large pool of volunteers for what the scientists call their “psychological valence,” a kind of measure of each word’s emotional temperature.

The volunteers ranked words they perceived as the happiest near the top of a 1-9 scale, with sad words near the bottom. Each word’s final score was calculated by averaging the volunteers’ responses. “Happy”, for example, ranked 8.30, “hahaha” 7.94, and “parks” 7.14. Neutral words like “and” and “the” scored 5.22 and 4.98. At the bottom were “trapped” 3.08, “crash” 2.60, and “jail” 1.76.

Using these scores, the team combed through the tweets of 4,688 users who publicly identify their location and were geotagged with latitude and longitude in the city of San Francisco (so they could pinpoint exactly which park they were tweeting from).

“Then, working with the U.S. Forest Service, we developed some new techniques for mapping vegetation of urban areas–at a very detailed resolution, about a thousand times more detailed than existing methods,” says study co-author Jarlath O’Neil-Dunne, director of UVM’s Spatial Analysis Laboratory in the UVM Rubenstein School of Environment and Natural Resources and a co-author on the new study.

“That’s what really enabled us to get an accurate understanding of how the greenness and vegetation of these urban areas relates to people’s sentiment there.”

Overall, the tweets posted from urban parks in San Francisco were 0.23 points happier on the hedonometer scale over the baseline. The increase is “equivalent to that of Christmas Day for Twitter as a whole in the same year,” the scientists write.

Exactly why parks have this effect on people isn’t fully understood — and wasn’t the object of the present study. Regardless of how it happens, the results suggest that people tend to be happier in nature. That’s a finding “that may help public health officials and governments make plans and investments,” says UVM’s Aaron Schwartz.

The paper “Visitors to urban greenspace have higher sentiment and lower negativity on Twitter” has been published in the journal People and Nature.