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Are green spaces happy places?

by on 2014/01/28

While we know that some of the lifestyle choices we make are good or bad for our health and mental wellbeing, we might be less inclined to think about how the environment we live in affects us. In recent years, however, there has been a growing interest in how factors in our environment, for example the amount of green space in the area we live, might influence a range of important outcomes, from physical health and stress to mortality. A recent study highlighted that although living in areas with more green space has been linked to a range of better health outcomes, much of this work has used information from a single assessment. That creates a problem, as noted by the authors of the study:

“Are people happier and healthier due to the proximity of green space to their homes, or do healthier people move to greener areas?”

By accessing information about people moving to or from greener areas and following those people for 3 years after their move, the new study reported that moving to a greener area not only led to an improvement in mental health, but that this was maintained over time. This positive effect of green space received coverage in a number of media outlets, including the Daily Mail, Guardian, and BBC News, for example.

What did the research say?

The study was able to investigate the question of how green space is associated with mental health by accessing data from the British Household Panel Survey (BHPS), a UK-wide survey of households which began in 1991 and continues as the Understanding Society survey. The researchers, all from the European Centre for Environment and Human Health, University of Exeter Medical School and led by Dr Ian Alcock, restricted their analyses to the English participants, as these households could be linked to the Generalised Land Use Database for England. This is a database that provides information about how the land in a defined area is used across 9 categories, including green space, water, buildings, roads, etc. So for the English participants in the BHPS, it was possible to calculate the proportion of their surrounding area classified as green space.

The research team also narrowed the analytical sample to include only those who had moved at some point during their participation, and who had 3 years of information both before and after their move. They noted that this was important so that they could track mental health both in the years leading up to someone moving and, more significantly, afterwards, to ensure any change in mental health was sustained (or indeed not). Moves were classified as either from green to less green, or vice versa, though were always urban areas to avoid confounding effects of moving to or from rural areas.

Mental health was assessed annually in the BHPS participants using a version of the General Health Questionnaire (GHQ), a screening tool often used in initial assessments of disorders such as anxiety and depression (when used in a clinical setting, if an individual’s score is below a specified cutoff, they would have a more detailed follow-up before the clinician would make any diagnosis). The GHQ is widely used in research studies, and the current study used the short, 12-item version. Participants completed 6 questions each for positive and negative mood states where they were specifically asked to report how their recent state (over the “past few weeks”) compared with what they would consider “usual” for them.

The results of the study suggested that people who moved to green areas had better GHQ scores, each year after their move, across the 3 years considered. The authors interpreted this positive change in their general level of mental health as being a result of their move. Importantly, this improvement was sustained; that is, it didn’t fall back to their earlier level once they adjusted to their new surroundings. Interestingly, participants who moved to less green areas had an immediate drop in their mental health in the assessment before their move, but they returned to their original level of mental health in the year after moving.

The authors of the study were careful to point out a number of issues in their analysis to avoid the findings being over-interpreted, for example, the need to restrict to a relatively small sample (just over 1000 individuals from a pool of over 5000 households) so that the relevant data were available over a number of years. In addition, they discussed how the nature of examining people who move introduces potential confounds (reasons for moving, other influences on mental health in these groups pre- and post-move), so another way to examine these associations would be to examine health in groups of people before and after urban developments in their area (making the area more or less green).

What did the media say?

The reporting of the study was generally very clear (Daily Mail, BBC News), probably because the authors were careful to explain their findings, and were quoted in the news reports of it. The media coverage generally paid less attention to the lack of a long-term negative effect of moving to less green areas, but as the authors had pointed out this aspect requires further work to better understand it, the focus on the positive effect of moving to greener areas is understandable.

The bottom line.

A better understanding of how our living environment affects our health, and particularly if that effect is maintained, is important. People can choose to take up or not various behaviours known to affect their health (and debates continue about the importance of free choice versus the consequences of such behaviours), but if environments can make us sick or well, the important question that the authors of the study were able to ask in the media coverage was “who is in control of that?” (see the BBC News report). Is it something policy makers need to take greater responsibility for, or if there are health benefits of more green space, should it become something that should be funded through the health service?

I. Alcock, M. P. White, B. W. Wheeler, L. E. Fleming and M. H. Depledge, (2014). “Longitudinal Effects on Mental Health of Moving to Greener and Less Green Urban Areas”. Environmental Science and Technology vol 48, pp 1247–1255 doi: 10.1021/es403688w

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