London - City dwellers should visit parks more often and take advantage of this free and easy way to boost their physical and mental health, environmental scientists have urged.
It found that bigger parks with more trees and vegetation – as well as plenty of flowers – had a more significant mood-boosting effect than smaller ones.
And the elevated mood that a visit to a park brings lasts "like a glow" for up to four hours afterwards, the researchers said.
The US study was based on an analysis of hundreds of tweets posted every day by people visiting 160 parks in San Francisco.
They used happier words and expressed less negativity on Twitter than before their visit, according to the scientists from the University of Vermont.
They found the overall rise in happiness was equivalent to that recorded on Christmas Day, which they said was the happiest day of the year on Twitter.
The effect suggests parks should be given greater priority by urban planners, they argue.
The findings were published in the journal People and Nature.
Dr Richard Fuller of NERP EDH and UQ says that research worldwide continues to discover the health benefits of being in nature. "For example, spending ten minutes in a park every day – even when we're not exercising in it – has been shown to lower our blood pressure."
Another study based in China found that a person's stress was significantly reduced after they exercise in a forest, compared with indoors. Related research in Switzerland also showed that exercising in parks reduces stress-induced headaches – the effect was the same if the person exercised in a forest.