Urban residential tree canopy and perceived stress among pregnant women

To examine the association of urban residential tree canopy cover with perceived stress in a cohort of pregnant women in Philadelphia, PA, and explore whether this association differed among participants with a history of anxiety and depression.

We performed a secondary analysis of 1294 participants of the Motherhood & Microbiome (M&M) pregnancy cohort who lived in Philadelphia, with first visit perceived stress (Cohen's Perceived Stress Scale, PSS-14), and key covariate data. Tree canopy cover was calculated as percent cover within 100 and 500 m radii buffers around participants' homes. We performed multilevel mixed effects linear regression models, with perceived stress as the dependent variable. The main independent variable was tree canopy coverage. Individual-level covariates included season of last menstrual period, history of depression or anxiety, race/ethnicity, insurance, parity, and age. Census tract neighborhood deprivation index was used to account for area-level socioeconomic confounding variables. We also examined whether a history of anxiety or depression, modified the association between tree canopy coverage and perceived stress.

Most participants were non-Hispanic Black (70.6%, n = 913), on Medicaid or uninsured (60.4%, n = 781), and 15.8% (n = 204) of participants had a prior history of depression or anxiety. We did not detect associations between tree canopy coverage and perceived stress overall. However, we detected effect modification; among participants with a history of depression or anxiety, each standard deviation increase in tree canopy cover was associated with lower PSS-14 in 100 m buffers (β -1.0, 95% CI -1.8, -0.2), but not among participants with no histories of depression or anxiety (β 0.2, 95% CI -0.3, 0.7) (interaction P = 0.007). Results were similar in directionality but not statistically significant within 500 m buffers.

Residential tree canopy coverage was associated with reduced perceived stress among urban-dwelling pregnant women with history of anxiety or depression. Future studies of the effects of greenness and other stress-reducing efforts should consider underlying mental health conditions as effect modifiers.