The results of a recent study of the University of Exeter gives extra support for all those who are committed to making the urban environment greener: the effects on your health are noticeable on the short term but continue to do their good work for a longer time (at least three years).

Meanwhile, a great number of nationwide and international studies (>70) have shown a positive relationship between nature and health. It is also clear from several studies that people living in the greenest urban areas in general have a better physical and mental health than people living in urban environments that are less green. Yet the question does arise, when discussing these results: are people happier and healthier thanks to nearby parks in the neighbourhood they live in, or do healthy people move to greener surroundings? It could also be that people who exercise more actively move to areas where more outdoor activities are available. Or it could be that the higher income of people with a sound mental health enables them to live in greener areas, where the prices of houses are often higher.

1000 British households were followed for five years

Environmental Science & Technology published the results of a University of Exeter survey into the long-term effects on people’s mental health when they move to either a greener, or an urban environment with less green spaces. For this study panel data was used of over 1,000 British households that had filled out the General Health Questionnaire (GHQ) for five consecutive years and, between the second and third year, moved to another urban area. This study is so special because the same people were followed over a longer period of time and lived in both greener and less green urban environments during that particular period.

In this study, corrections were made for the effects of a great number of factors that could also potentially influence mental health and the outcome of the survey. For example, for the various areas, the statistics for unemployment and criminality were taken into account. On a more individual level there were corrections for: education, work status, marital status, type and size of the dwelling, but also personality traits. Additionally, the motives of the group that went to an area with less parks and the one that went to greener surroundings were looked into. These appear to be fairly similar. The most often-mentioned motive for both groups was a larger house (even for those who moved to areas with less green).

Important results for policy makers and urban planners

From the study of the University of Exeter it appears that people who move to a greener area on average immediately show an improvement in mental health and are able to retain this in the coming years.

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Research project leader Doctor Ian Alcock thinks that the results of the study could have a significant impact: ‘We’ve shown that individuals who move to greener areas have significant and long-lasting improvements in mental health. These findings are important for urban planners thinking about introducing new green spaces to our towns and cities, suggesting they could provide long-term and sustained benefits for local communities.’ (Science Daily, 2014)

During the study two moments were selected to measure the status quo of the respondents, before the move was made. This allowed the researchers to look into possible effects of anticipation that can appear prior to a change (such as happiness over the move to a greener urban area, or sadness when moving to an area with more bricks and concrete). With the group moving to a greener neighbourhood, the final measurement before the move already shows a rising line in the health score. With the group moving to an area that is not so green, there is a significant decline in the health score, prior to the move. However, after these groups were moved, the mental health appears to repair to the point of departure (see figure below). These results seem to indicate that people adapt pretty quickly to living in a less green environment.

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Based on earlier research, it was expected that the move to a less greener environment would lead to a permanently lower mental health score in the years following the move. And an equal, yet contrary, effect to the group moving to a greener area. No explanation can be found in the study for the absence of this effect. The researchers indicate that a possible explanation could be that people, experiencing a worsened mental health over the years, no longer participate in the GHQ in subsequent years, the so-called non-respondents. The results could appear more positive than they are because the only data that was used for this study is that of respondents having filled out the questionnaires in the five consecutive years. However, the number of respondents is too small to make such conclusions. It would take a follow-up survey with a larger number of respondents.

Again, evidence has shown that green in the city is important

Although a follow-up study is still necessary, co-author Doctor Mathew White indicates this investigation does contribute to our insight in the working mechanism of nature as a source for improving our health and well-being: ‘We needed to answer important questions about how the effects of green space vary over time. Do people experience a novelty effect, enjoying the new green area after the move, but with the novelty then wearing off? Or do they take time to realise the benefits of their new surroundings as they gradually get to know local parks? What we’ve found suggests that the mental health benefits of green space are not only immediate, but sustainable over long periods of time.’ (Science Daily, 2014)

The outcome of this survey adds another important piece to the puzzle. If and when the puzzle will ever be completed is yet to be seen. Because it is difficult to say how many pieces will ever complete it (how many follow-up research is needed). What is clear, however, is that there is a more and more proof for the positive effects of plants on our health, and for longer periods of time, too. In other words: it pays off to invest in green!

Check out the video where Doctor Ian Alcock explains the survey and its significance.


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