Tweets show how a stroll in the park can bring happiness

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“THERE ARE moments,” wrote Henry David Thoreau, “when all anxiety and stated toil are becalmed in the infinite leisure and repose of nature.” Thoreau, who famously spent two years living alone in a forest cabin near Walden Pond in Massachusetts, understood the restorative powers of nature. But one need not flee to the wilderness to benefit from Earth’s natural beauty. New research suggests that a stroll through a neighbourhood park can boost one’s mood. The greener the park, the bigger the effect.

It may seem like common sense that spending time outdoors improves our state of mind. But evidence for such a link is sparse. Studies have found that greener neighbourhoods are associated with lower levels of depression. Children who grow up around green space are less likely to develop psychiatric disorders. When asked to visit green spaces, research subjects report higher levels of well‐being. And yet demonstrating an empirical relationship between nature and happiness has proved difficult.

A new paper by researchers at the University of Vermont attempts to do this using data from social-media posts. The authors compiled a list of Twitter users who had posted a tweet within the boundaries of a park or other green space in San Francisco between May and August 2016. From this list of nearly 5,000 Twitter users, the authors collected tweets published during the hours before, during and after their park visit. These tweets were analysed using the Hedonometer, a tool designed to measure the sentiment of social-media content. This tool, which is based on a database of more than 10,000 words rated on a scale from 1 (least happy) to 9 (most happy), has been used in previous academic studies and correlates with traditional survey-based measures of well‐being.

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The authors found that tweets published while visiting a park were about 4% “happier” than those published before or after the visit (see chart). This improvement in sentiment, the authors point out, is comparable to that observed across Twitter on Christmas Day. Park-goers became less self-centred and more positive: use of the word “me” dropped by 38%; negative words like “no”, “not” and “don’t” also fell. Bigger parks and parks with higher levels of greenery led to a bigger increase in tweet “happiness”. Such apparent contentment lingered for at least an hour.

Exposure to nature appears to improve mental health. Yet much of the world is set to urbanise rapidly in the coming years. Today just over half of the world’s population lives in cities; by 2050 the UN reckons it will be 68%. As cities grow ever more populated, green spaces may get squeezed out. “With most of the planet’s population now living in cities,” the authors conclude, “we must find ways to bring nature to them.” Thoreau would surely agree.