Residential green space in childhood is associated with lower risk of psychiatric disorders from adolescence into adulthood

Kristine Engemann

PNAS March 12, 2019 116 (11) 5188-5193

Significance

Growing up in urban environments is associated with risk of developing psychiatric disorders, but the underlying mechanisms are unknown. Green space can provide mental health benefits and possibly lower risk of psychiatric disorders. This nation-wide study covering >900,000 people shows that children who grew up with the lowest levels of green space had up to 55% higher risk of developing a psychiatric disorder independent from effects of other known risk factors. Stronger association between cumulated green space and risk during childhood constitutes evidence that prolonged presence of green space is important. Our findings affirm that integrating natural environments into urban planning is a promising approach to improve mental health and reduce the rising global burden of psychiatric disorders.

Abstract

Urban residence is associated with a higher risk of some psychiatric disorders, but the underlying drivers remain unknown. There is increasing evidence that the level of exposure to natural environments impacts mental health, but few large-scale epidemiological studies have assessed the general existence and importance of such associations. Here, we investigate the prospective association between green space and mental health in the Danish population. Green space presence was assessed at the individual level using high-resolution satellite data to calculate the normalized difference vegetation index within a 210 × 210 m square around each person’s place of residence (∼1 million people) from birth to the age of 10. We show that high levels of green space presence during childhood are associated with lower risk of a wide spectrum of psychiatric disorders later in life. Risk for subsequent mental illness for those who lived with the lowest level of green space during childhood was up to 55% higher across various disorders compared with those who lived with the highest level of green space. The association remained even after adjusting for urbanization, socioeconomic factors, parental history of mental illness, and parental age. Stronger association of cumulative green space presence during childhood compared with single-year green space presence suggests that presence throughout childhood is important. Our results show that green space during childhood is associated with better mental health, supporting efforts to better integrate natural environments into urban planning and childhood life.

日本語訳

都市住宅はいくつかの精神障害の高リスクと関連しているが、根本的な要因は知られていないままである。自然環境が精神的健康に与える影響の証拠は増加しているが、いくつかの大規模な疫学研究ではそのような協会の重要性や一般的な存在が評価されているものは少ない。ここでは、デンマークの人口における精神的健康と緑地の関連性についての課題を調査する。緑地の存在は、個人レベルで使われている衛星の高解像度データで評価され、10歳までのそれぞれの住人に対し　210×210m　の正規化差植生指数を計算した。

【Normalized Difference Vegetation Index（正規化差植生指数）とは植生の分布状況や活性度を示す指標である】

幼児期の高いレベルでの緑地の存在は人生の後半に広範囲における精神的障害の低リスクとの関連性を示している。幼児期に低いレベルでの緑地に住んでいた人々はその後の精神的疾患の危険性が高いレベルでの緑地に住んでいた人々に比べ様々な障害にわたって55％も高かった。その関連性は都市化、経済的要因、両親の精神疾患の病歴、両親の年齢などを合わせた後でも維持された。一年間の緑地の存在と比べ、累積的な幼児期の緑地の存在の強い関連性は、幼児期の間ずっと緑地の存在があることが重要だと示唆している。それらの結果は、幼児期の緑地がよりよい精神的健康と関連性があることを示しており、都市計画と、子供たちの生活によりよい自然環境を統合することを支援をしている。