p u b l i c h e a l t h 1 2 7 ( 2 0 1 3 ) 1 0 0 5 e1 0 1 1
Available online at www.sciencedirect.com
Public Health journal homepage: www.elsevier.com/puhe
Original Research
An ecological study investigating the association between access to urban green space and mental health D. Nutsford a,*, A.L. Pearson b, S. Kingham a a b
University of Canterbury, GeoHealth Laboratory, Christchurch, New Zealand University of Otago, Department of Public Health, Wellington, New Zealand
article info
abstract
Article history:
Objectives: This study aims to find whether proximity to urban green spaces is associated
Received 14 January 2013
with human mental health.
Received in revised form
Study design: A cross-sectional examination of the relationship between access to urban
31 July 2013
green spaces and counts of anxiety/mood disorder treatments amongst residents (aged 15
Accepted 27 August 2013
years and over) in Auckland City, New Zealand.
Available online 19 November 2013
Methods: Anxiety/mood disorder treatment counts by three age groups were aggregated to 3149 small area units in Auckland. Six measures of green space access were derived using
Keywords:
GIS techniques involving total green spaces and useable green spaces. Negative binomial
Green space
regression models have been fitted to test the relationship between access to green space
Mental health
and area-level anxiety/mood disorder treatment counts, adjusted for age and area-level
Geographic Information Systems
deprivation.
Urban planning
Results: Anxiety/mood disorder treatment counts were associated with three green space
Accessibility
measures. The proportion of both total and useable green space within 3 km and distance to nearest useable green space all indicated a protective effect of increased access to green space against anxiety/mood disorder treatment counts. Access to total and useable green space within 300 m did not exhibit significant associations. Conclusion: This study found that decreased distance to useable green space and increased proportion of green space within the larger neighbourhood were associated with decreased anxiety/mood disorder treatment counts in an urban environment. This suggests the benefits of green space on mental health may relate both to active participation in useable green spaces near to the home and observable green space in the neighbourhood environment. ª 2013 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.
* Corresponding author. GeoHealth Laboratory, Dept. of Geography, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand. Tel.: þ64 3 364 2987x7936; fax: þ64 3 364 2907. E-mail addresses: [email protected], [email protected] (D. Nutsford). 0033-3506/$ e see front matter ª 2013 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.puhe.2013.08.016
1006
p u b l i c h e a l t h 1 2 7 ( 2 0 1 3 ) 1 0 0 5 e1 0 1 1
Introduction As many cities experience poor air quality, water pollution, heat island effects and crowding,1 it is un-surprising that the physical and increasingly, the mental health of urban residents has become of major focus in recent decades. One area of investigation is the relationship between access to urban green space and both physical and mental health benefits.2e14 An ‘integrated area comprising natural, semi natural, or artificial green land’,13,p174 urban green space provides an aesthetic place for social and recreational opportunities, which encourages physical activity, enhances social ties and promotes mental and physical recuperation.13,15 The majority of green space studies evaluate its influence on physical health or general health as the health outcome. Many include a mental health component, but present conflicting findings.5,8,12,16 Importantly, studies in New Zealand found no association between green space and a number of health outcomes, including physical health and cause-specific mortality.8,12 This suggests that green space and any associations with health outcomes may vary between environments and social contexts,8 for example the role of green space is likely to be more influential within urban environments in contrast to rural areas. Green space research concluded that New Zealand’s relative prevalence of natural, green environments and a culture of ‘outdoor holidaying’ in comparison to other regions may reduce the ability to detect associations with health outcomes.8 However, this claim has not been evaluated in relation to mental health. A review of health associations with urban green space concluded that many claims are supported by weak evidence and studies were limited by poor design and failure to exclude confounding factors and bias.1 Much less established is the investigation of the effects of access to and visualization of green space on mental health. General consensus in existing literature finds green space to be negatively associated with poor mental health,5,11 however it is met with some contention and the causal pathways remain relatively unexplored.1,2 Mental health is important as it is often a precursor for other chronic conditions and physical health outcomes.17 In New Zealand, approximately 20% of the population suffered from a mental disorder in a 12-month period,18 while anxiety and mood disorders affect 5.7% of Auckland’s population.17 Given the contribution of mental illness to the disease burden in New Zealand, it is important to evaluate potentially amenable aspects of neighbourhood environments which might reduce this burden. Three primary theoretical pathways have been identified through which green space may influence mental health.13,15 First, recreational physical activity, common in green space, promotes positive moods and reduces stress levels.19 Second, both planned and coincidental social interaction often take place in public green spaces and have been shown to improve mental well-being.13 Third, green spaces are seen as places for relaxation and recuperation from stressful activities, which influences stress hormone levels.11 Due to the difficulty in obtaining population-level mental health data, most studies rely on self-reported mental health scoring,20e23 which often under-estimates mental illness.24
Although some studies have reported no direct relationship between green space and mental health outcomes,2 others have found that active participation in green space,19 the proportion of5,10,19,20 and distance to green space,14 and perceived greenness21 were significantly, positively associated with mental health indicators. For example, a Danish study found that individuals living more than 1 km from green space were 1.42 times more likely to experience stress than individuals living
Available online at www.sciencedirect.com
Public Health journal homepage: www.elsevier.com/puhe
Original Research
An ecological study investigating the association between access to urban green space and mental health D. Nutsford a,*, A.L. Pearson b, S. Kingham a a b
University of Canterbury, GeoHealth Laboratory, Christchurch, New Zealand University of Otago, Department of Public Health, Wellington, New Zealand
article info
abstract
Article history:
Objectives: This study aims to find whether proximity to urban green spaces is associated
Received 14 January 2013
with human mental health.
Received in revised form
Study design: A cross-sectional examination of the relationship between access to urban
31 July 2013
green spaces and counts of anxiety/mood disorder treatments amongst residents (aged 15
Accepted 27 August 2013
years and over) in Auckland City, New Zealand.
Available online 19 November 2013
Methods: Anxiety/mood disorder treatment counts by three age groups were aggregated to 3149 small area units in Auckland. Six measures of green space access were derived using
Keywords:
GIS techniques involving total green spaces and useable green spaces. Negative binomial
Green space
regression models have been fitted to test the relationship between access to green space
Mental health
and area-level anxiety/mood disorder treatment counts, adjusted for age and area-level
Geographic Information Systems
deprivation.
Urban planning
Results: Anxiety/mood disorder treatment counts were associated with three green space
Accessibility
measures. The proportion of both total and useable green space within 3 km and distance to nearest useable green space all indicated a protective effect of increased access to green space against anxiety/mood disorder treatment counts. Access to total and useable green space within 300 m did not exhibit significant associations. Conclusion: This study found that decreased distance to useable green space and increased proportion of green space within the larger neighbourhood were associated with decreased anxiety/mood disorder treatment counts in an urban environment. This suggests the benefits of green space on mental health may relate both to active participation in useable green spaces near to the home and observable green space in the neighbourhood environment. ª 2013 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.
* Corresponding author. GeoHealth Laboratory, Dept. of Geography, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand. Tel.: þ64 3 364 2987x7936; fax: þ64 3 364 2907. E-mail addresses: [email protected], [email protected] (D. Nutsford). 0033-3506/$ e see front matter ª 2013 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.puhe.2013.08.016
1006
p u b l i c h e a l t h 1 2 7 ( 2 0 1 3 ) 1 0 0 5 e1 0 1 1
Introduction As many cities experience poor air quality, water pollution, heat island effects and crowding,1 it is un-surprising that the physical and increasingly, the mental health of urban residents has become of major focus in recent decades. One area of investigation is the relationship between access to urban green space and both physical and mental health benefits.2e14 An ‘integrated area comprising natural, semi natural, or artificial green land’,13,p174 urban green space provides an aesthetic place for social and recreational opportunities, which encourages physical activity, enhances social ties and promotes mental and physical recuperation.13,15 The majority of green space studies evaluate its influence on physical health or general health as the health outcome. Many include a mental health component, but present conflicting findings.5,8,12,16 Importantly, studies in New Zealand found no association between green space and a number of health outcomes, including physical health and cause-specific mortality.8,12 This suggests that green space and any associations with health outcomes may vary between environments and social contexts,8 for example the role of green space is likely to be more influential within urban environments in contrast to rural areas. Green space research concluded that New Zealand’s relative prevalence of natural, green environments and a culture of ‘outdoor holidaying’ in comparison to other regions may reduce the ability to detect associations with health outcomes.8 However, this claim has not been evaluated in relation to mental health. A review of health associations with urban green space concluded that many claims are supported by weak evidence and studies were limited by poor design and failure to exclude confounding factors and bias.1 Much less established is the investigation of the effects of access to and visualization of green space on mental health. General consensus in existing literature finds green space to be negatively associated with poor mental health,5,11 however it is met with some contention and the causal pathways remain relatively unexplored.1,2 Mental health is important as it is often a precursor for other chronic conditions and physical health outcomes.17 In New Zealand, approximately 20% of the population suffered from a mental disorder in a 12-month period,18 while anxiety and mood disorders affect 5.7% of Auckland’s population.17 Given the contribution of mental illness to the disease burden in New Zealand, it is important to evaluate potentially amenable aspects of neighbourhood environments which might reduce this burden. Three primary theoretical pathways have been identified through which green space may influence mental health.13,15 First, recreational physical activity, common in green space, promotes positive moods and reduces stress levels.19 Second, both planned and coincidental social interaction often take place in public green spaces and have been shown to improve mental well-being.13 Third, green spaces are seen as places for relaxation and recuperation from stressful activities, which influences stress hormone levels.11 Due to the difficulty in obtaining population-level mental health data, most studies rely on self-reported mental health scoring,20e23 which often under-estimates mental illness.24
Although some studies have reported no direct relationship between green space and mental health outcomes,2 others have found that active participation in green space,19 the proportion of5,10,19,20 and distance to green space,14 and perceived greenness21 were significantly, positively associated with mental health indicators. For example, a Danish study found that individuals living more than 1 km from green space were 1.42 times more likely to experience stress than individuals living
