UC Davis

PURPOSE: Exposure to nature, particularly vegetation (greenness), may be beneficial for mental health. We investigated whether higher surrounding greenness in early life was associated with subsequent reduced risk of depressive symptoms and whether this association was modified by age, sex, or population density. METHODS: Participants from the Growing Up Today Study were included if they reported on depressive symptoms between 1999 and 2013. Greenness exposure was characterized as the cumulative average normalized difference vegetation index value (1000 m resolution) from 1989 until 2 years before outcome assessment or age 18 based on geocoded addresses. We defined high depressive symptoms as the top 10% of scores on the McKnight Risk Factor Survey or the Center for Epidemiologic Studies of Depression scale, depending on the questionnaire. Data were analyzed using Cox proportional hazards model adjusted for socioeconomic status and other confounders. RESULTS: There was a 6% lower incidence of high depressive symptoms associated with an interquartile range increase in greenness (95% confidence interval, 11%-0%). This relationship was stronger in higher population density areas (>1000 people/mi2, 8% lower incidence, 95% confidence interval 15%-1%). CONCLUSIONS: Living in an area with greater surrounding greenness during childhood may be beneficial for mental health, particularly in more urban areas.