This study investigated whether the presence of green space during childhood is associated with the risk of developing psychiatric disorders later in life. The study also sought to determine if and to what extent the amount of green space exposure during childhood changed the overall effect regarding the risk for later psychiatric disorders. A third aim of the study was to examine if green space presence at a specific age during childhood would have an effect on the risk of psychiatric disorders later in life.
The study considered data on all persons born in Denmark from 1985 to 2003 and who were alive and still living in Denmark at their 10th birthday. Data examined for each individual included place of residence, socioeconomic status, parental history of mental illness, parental age, and presence of green space during childhood. Green space presence was based on remote sensing measurements (the normalized difference vegetation index) within a 210 × 210 meter square around each individual's place of residence from birth to age 10. Researchers linked this data with information from the Danish Psychiatric Central Research Register about psychiatric disorders developed after the study participants' 10th birthday. The Register includes information on admissions to Danish psychiatric in-patient facilities and out-patient visits to psychiatric departments or emergency care. Denmark has no private psychiatric in-patient facilities, and treatment for psychiatric disorders is free.
By linking individual longitudinal data on mental health outcomes with levels of childhood green space, researchers found that children living with higher levels of green space had lower risks of developing psychiatric disorders during adolescence or adulthood. Except for intellectual disability and schizoaffective disorders, children living at the lowest levels of green space had a 15 to 55% higher risk of developing psychiatric disorders than children living at the highest levels of green space. The strongest association between risk and green space presence was in more highly-urbanized areas, while the weakest association was in rural areas. Risk was also generally higher for cumulated green space presence compared with green space at age 10. These findings indicate a dose-response effect, meaning that the protective effects of green space on mental health outcomes was greater for higher levels of greenspace. There was no evidence of green space presence at a specific age during childhood having a special effect on the risk of psychiatric disorders later in life. What the study does indicate is that green space presence is important throughout the childhood years.
This study suggests that green space presence during childhood may help protect individuals from psychiatric disorders during adolescence and adulthood. This protective association remained after adjusting for other known risk factors, such as urbanization, socioeconomic factors, family history of mental illness, and parental age. The association was similar in strength, or sometimes stronger, than associations between mental health and other known risk factors, such as socioeconomic status, prior history of mental illness, and age. Finally, the association was somewhat stronger for the development of mental illness in adolescence vs. adulthood.
Overall, the results of this study are consistent with other studies reporting positive impacts of green space on mental health and support efforts to integrate natural environments into the lives of children, especially in urban environments where access to nature tends to more limited.