Presence of nature in our living environment is associated with a range of mental health benefits. High levels of residential green space have been associated with lower rates of mental ill-health indicators, for example, anxiety (Nutsford et al., 2013), stress (Fan et al., 2011), psychological distress (Sturm and Cohen, 2014), major depressive disorders (Mukherjee et al., 2017; Sarkar et al., 2018), antidepressant prescription rates (Taylor et al., 2015), and suicide risk (Helbich et al., 2018). Residential green space has also been shown to be positively associated with indicators of positive mental health, such as life satisfaction (Fleming et al., 2016), happiness (Van Herzele and de Vries, 2012) and subjective and psychological well-being (Mavoa et al., 2019; Sugiyama et al., 2008; White et al., 2017; Wood et al., 2017).

Reviews of studies on the relationship between green space and mental health have identified a common shortcoming of this evidence, namely the preponderance of cross-sectional study designs (Frumkin et al., 2017; Hartig et al., 2014). Cross-sectional studies are effective at identifying and measuring the strength of associations between green space and mental health, however, such studies lack temporality, which is an absolute requirement for causation. Hence, there have been repeated calls for a greater representation of longitudinal study designs within green space and mental health research (Frumkin et al., 2017; Hartig et al., 2014). In response to this call, a number of studies have used nationally representative, longitudinal surveys, such as the British Household Panel Survey, to investigate how residential green space influences mental health across the life-course and by gender (Astell-Burt et al., 2014) or how moving to greener residential areas affects mental health (Alcock et al., 2014). Younan et al. (2016) used a two wave cohort of adolescents in the USA to show that increased exposure to local urban green space was related to lower aggression. Richardson et al., 2017, using longitudinal survey data of urban-dwelling children in Scotland, found that access to green space was related to social and emotional development as measured by the Strengths and Difficulties Questionnaire. Dadvand et al. (2015) carried out repeated assessments of cognitive development among school children (ages 7–10) in Spain and found that urban green space exposure was associated with increased attention and working memory. These longitudinal studies have strengthened the evidence for causal inference about the role green space plays in mental health outcomes.