Green City: Why Nature Matters to Health – An Evidence Review

This report focuses on the impact green space has on health outcomes and the characteristics that may modify the impacts. The meta-narrative systematic review includes literature that examines urban green space and physical health, mental health and wellbeing. 
The 106 studies included in the review cover a wide range of health outcomes and green space types. The methodological quality of each study was assessed. The number of studies published by year show a increasing interest in the topic - almost 75% were published since 2008, with 24% published in 2013 alone. 
Overall, 78% of the associations investigated were found to be statistically significant for a positive relationship between green space and at least one aspect of health. The relationship between mental health and green space was most consistent; 92% of the studies found a statistically significant relationship. The overall strength of these studies was assessed as fair. A majority (67%) of studies that looked at aspects of physical health found statistically significant relationships as well. The overall strength of these studies was good, higher than the mental health studies. A large majority (79%) of studies that investigated wellbeing and green space also found significant, positive relationships. The overall strength of these studies was fair.
In all of the health outcomes, the studies that did not find a statistically significant relationship between green space and health had a lower quality than the ones that found a significant relationship.
The main conclusions of this review are:  Green space improves physical health, mental health and wellbeing of urban residents.  Frequent access to nearby green space is important, especially for children.   Nearby green space may provide added benefit in low-income neighbourhoods.   Green space that is perceived as unsafe and poorly maintained does not provide health benefits.