This study presents a new approach to investigate the urban-rural differences in schizophrenia risk by focussing on the association between natural environments, also known as green space, and schizophrenia risk.

2018.06.14 | Annette Bang Rasmussen

Kristine Engemann Jensen, postdoc, Dept. of Ecoinformatics and Biodiversity, Aarhus University

About the study

Schizophrenia risk has been linked to urbanization, but the underlying mechanism remains unknown. Green space is hypothesized to positively influence mental health and might mediate risk of schizophrenia by mitigating noise and particle pollution exposure, stress relief, or other unknown mechanisms. The objectives for this study were to determine if green space is associated with schizophrenia risk, and if different measures of green space associate differently with risk. We used satellite data from the Landsat program to quantify green space in a new data set for Denmark at 30×30m resolution for the years 1985-2013. The effect of green space at different ages and within different distances from each person’s place of residence on schizophrenia risk was estimated using Cox regression on a very large longitudinal population-based sample of the Danish population (943 027 persons). Living at the lowest amount of green space was associated with a 1.52-fold increased risk of developing schizophrenia compared to persons living at the highest level of green space. This association remained after adjusting for known risk factors for schizophrenia: urbanization, age, sex, and socioeconomic status. The strongest protective association was observed during the earliest childhood years and closest to place of residence. This is the first nationwide population-based study to demonstrate a protective association between green space during childhood and schizophrenia risk; suggesting limited green space as a novel environmental risk factor for schizophrenia. This study supports findings from other studies highlighting positive effects of exposure to natural environments for human health.

Facts about the study

• Exposure to more green space during childhood is associated with lower risk of schizophrenia
• Risk decreased in a dose-response association with increasing green space exposure even after adjusting for confounding effects of urbanization, socioeconomic status, age, and sex
• The strongest protective association of green space was found within the closest distance to a person’ residence
• Exposure during the earliest years of childhood were most strongly associated with the risk of schizophrenia

The paper "Childhood exposure to green space - A novel risk-decreasing mechanism for schizophrenia?" was published in Schizophrenia Research in March 2018.

Further information

Kristine Engemann, Department of Ecoinformatics and Biodiversity Aarhus University, Engemann@bios.au.dk

Carsten Bøcker Pedersen, National Center for Register Research Aarhus University, cbp@econ.au.dk