Urban greenspace is associated with reduced psychological stress among adolescents: A Geographic Ecological Momentary Assessment (GEMA) analysis of activity space

Highlights

• Geographic EMA is used to investigate the synchronous greenspace-stress association.

• Urban greenspace is associated with reduced psychological stress for adolescents.

• The association occurs only when the adolescent is away from home.

• The association does not differ by sex, season, or emotional dysregulation.

Abstract

This study investigates the momentary association between urban greenspace, captured using Normalized Difference Vegetation Index (NDVI) derived from Landsat imagery, and psychological stress, captured using Geographic Ecological Momentary Assessment (GEMA), in the activity spaces of a sample of primarily African American adolescents residing in Richmond, Virginia. We employ generalized estimating equations (GEE) to estimate the effect of exposure to urban greenspace on stress and test for moderation by sex, emotional dysregulation, season, neighborhood disadvantage, and whether the observation occurs at home or elsewhere. Results indicate that urban greenspace is associated with lower stress when subjects are away from home, which we speculate is due to the properties of stress reduction and attention restoration associated with exposure to natural areas, and to the primacy of other family dynamics mechanisms of stress within the home. Subjects may also seek out urban greenspaces at times of lower stress or explicitly for purposes of stress reduction. The greenspace-stress association away from home did not differ by sex, emotional dysregulation, neighborhood disadvantage, or season, the latter of which suggests that the observed greenspace-stress relationship is associated with being in a natural environment rather than strictly exposure to abundant green vegetation. Given the association of urban greenspace with lower stress found here and in other studies, future research should address the mediated pathways between greenspace, stress, and stress-related negative health outcomes for different population subgroups as a means toward understanding and addressing health disparities.

Introduction

Psychological stress is a risk factor not only for mental disorders such as depression and anxiety, but also for a wide range of other ailments, including stroke, heart attack, and substance use disorders (Iwata et al., 2013, O’Donnell et al., 2016, Rosengren et al., 2004, Sinha, 2008). Recent research indicates that exposure to vegetation and natural areas can mitigate psychological stress by providing opportunities for physical activity and social interaction, as well as by engendering cognitive and physiological responses associated with psychological stress reduction and attention restoration following stressful experiences (Bratman, Hamilton, & Daily, 2012 Hartig, Mitchell, de Vries, & Frumkin, 2014). Such effects may be particularly pronounced for those living in urban areas, where exposure to urban vegetated or natural areas, referred to as ‘urban greenspace,’ may be limited. Indeed, research indicates that city residents have a higher level of psychological stress as compared to those living in rural areas (Dhingra et al., 2009, Lambert et al., 2015, Verheij et al., 2008). This is of particular concern given both the increasing concentration of the world’s population in cities (Turner, Nakamura, & Dinetti, 2004) and inequities in exposure and access to urban greenspace (Wolch, Byrne, & Newell, 2014). Understanding the relationship between greenspace and psychological stress among urban residents is thus of utmost concern for the development of interrelated policies on urban health, environmental justice, and greenspace infrastructure (Maller et al., 2006, Sullivan and Chang, 2011, WHO (World Health Organization), 2012).

Most observational studies of urban greenspace and psychological stress or other indicators of mental health, however, have been limited to measures of greenspace exposure based on the residential neighborhood, or where measures of greenspace exposure and stress are asynchronous or are derived from recall-based surveys (e.g. Feda, Seelbinder, Baek, & Raja, 2015; Maas et al., 2006, Markevych et al., 2014). Notably, the focus on the residential neighborhood may not adequately capture the actual exposure to an environmental condition, such as greenspace, and its effect on health, which can occur not only at the home location but also throughout an individual’s activity space, i.e. the routine places visited throughout daily life (Browning and Soller, 2014, Kwan and M.- P., 2012, Mennis and Mason, 2011). Further, recall based methods of recording the effect of contextual conditions on mood or psychological state, such as stress, are prone to error due to the lapse of time between environmental exposure and reporting (Shiffman, Stone, & Hufford, 2008).

In the present study, we aim to address these study design limitations in an investigation of the association between urban greenspace and psychological stress that utilizes in-situ and synchronous activity space-based measurements of greenspace exposure and stress. Unlike the majority of research on greenspace and mental health, which focuses on adults (Beyer et al., 2014, Roe et al., 2013, White et al., 2013), we focus here on a relatively understudied population: urban, African American adolescents. Adolescents in the U.S. report similar rates of stress as adults, which can act as a catalyst for negative health outcomes over the lifespan (APA, 2014). Mechanisms of stress for adolescents may differ from adults, however, as adolescence marks a critical developmental period, and carries a unique set of physical, sociological, and psychological stressors. As compared to adolescents generally, urban, African American adolescents may be particularly prone to additional contextual social and environmental stressors, as many African American urban neighborhoods exhibit concentrated economic disadvantage and disorder, with attendant high levels of crime, substance use, and physical decay (Brenner et al., 2013, Latkin and Curry, 2003, Mennis et al., 2016). Investigating the role of urban greenspace as a potential stress reducer among African American youth can contribute to a better understanding of the complex contextual mechanisms that influence stress among urban adolescents exposed to stressful environmental stimuli.

We use Geographic Ecological Momentary Assessment (GEMA), an approach integrating conventional EMA with Global Positioning Systems (GPS) and Geographic Information Systems (GIS), to capture and link momentary data on exposure to greenspace and psychological stress in the activity spaces of a sample of urban youth residing in Richmond, Virginia. Our primary research question is: Is exposure to urban greenspace associated with lower stress among a sample of urban, primarily African American, adolescents? Additionally, we inquire whether this association differs according to characteristics of the individual adolescent and environmental context of the observation. We employ generalized estimating equations (GEE) to estimate the effect of exposure to urban greenspace on stress, while controlling for demographic characteristics. We employ tests of moderation to investigate whether this association differs according to characteristics of the individual and the environmental contexts within which the association is observed.