The primary aim of this study was to assess the impact of changes in the amount and quality of neighborhood greenery on walking, cycling, and mental health of severely economically-disadvantaged adolescents and adults in the Netherlands. The study also aimed to investigate potential effects of greenery on subgroups within this population. A third aim was to explore residents' perceptions of green spaces as potentially influencing the outcomes of changes in greenery.
Data collection measures included an internet questionnaire administered at two different times – one before the changes in neighborhood greenery and one after the changes. A total of 401 adolescents (aged between 12 and 15 years) and 454 adults completed the questionnaire for both the first and second measurements. Items on the questionnaire addressed physical activity, perceptions of neighborhood greenery, and symptoms of depression, as well as demographic and socioeconomic characteristics of the participants.
For the physical activity items, a distinction was made between active transport (walking or cycling to get from one place to another) and physical activity in leisure time. The Center for Epidemiologic Studies–Depression Scale was used to assess depressive symptoms, and selected items from The Neighborhood Walkability Scale were used to assess participants' perceptions of neighborhood greenery. Three additional items were added to the questionnaire for the second measurement. These items specifically addressed the perceived improvement and use of greenery in the neighborhood environment, as a way to investigate if the perception could possibly serve as a mediator between greenery improvements and mental health.
A standardized questionnaire and face-to-face interviews with local district managers involved in the greenery interventions were used to collect objective information about changes in greenery in the targeted neighborhoods. The questionnaire listed 18 different types of greenery-intervention activities implemented for more than one year.
An analysis of the data indicated that, overall, there were small and non-significant associations between objective changes in greenery and changes in measured outcomes, with two major exceptions. Greenery interventions were associated with a smaller decline in leisure cycling among adolescents, and improvements in perceived natural elements were associated with a decrease in symptoms of depression in adults. An analysis of changes in subgroups identified some positive outcomes associated with educational level, gender, and age. These subgroup outcomes included (1) more leisure time walking by male adolescents and older adults, and (2) walking for active transport by highly educated adolescents and native Dutch adults.
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