In a recent study, increased street view-based green space, especially tree coverage, led to decreased risks of depression in post partum women, with mediation effects observed for physical activity.
According to a recent study published in The Lancet Regional Health–Americas, post partumdepression (PPD) risk is reduced by street view-based green space and physical activity (PA).
PPD is experienced by about 13% of new mothers in the United States and 20% of women in low- and middle-income countries. Stress, hormonal fluctuations, and other biological and psychosocial factors all contribute to depression in the post partum period, which has led to associated short- and long-term adverse outcomes.
Studies have indicated humans inherently require a connection with nature, and that affiliation with nature may improve emotional stability and stress recovery. While studies have linked green space exposure with improved stress, depression, and general mental health, this data mostly comes from a general population.
Data is lacking on the association between green space exposure and mental health in post partum women. PA is also a key factor in linking green space and mental health, but the role of PA on this relationship in post partum women is unclear.
To determine the association between green space exposure and PPD and how PA affects this association, investigators conducted a retrospective cohort study using electronic health records (EHRs) of over 430,000 singleton pregnancies at Kaiser Permanente Southern California (KPSC) facilities from 2008 to 2018. All participants lived in urban areas.
KPSC is comprised of a variety of sociodemographic populations from Southern California. A total of 415,020 singleton pregnancies were included in the analysis. Exclusion criteria included not being a KPSC member, having a gestational age below 20 weeks or above 47 weeks, having multiple births or still birth, and not having a residential address.
PPD was the primary outcome of the study, which was determined by KPSC using 2019 depression guidelines. Measurement was performed using the Edinburgh Postnatal Depression Scale (EPDS), with an EPDS score of 10 or higher indicating minor or major depressive disorder.
To ensure accuracy, depression diagnostic codes were used alongside a prescription for medications against depression within 12 months following deliveryto determine PPD.
Street view-based measures, satellite-based measures, and nearest park proximity were used to assess green space exposures. Street view-based measures include total street green space, tree, low-lying vegetation, and grass, while satellite-based measures include normalized difference vegetation index (NDVI), land-cover based green space, and tree canopy cover.
Participants self-reported PA data during visit encounters, responding to questions on number of days exercised per week and number of minutes exercised per day. This data was used to measure PA during pregnancy.
Of patients, the mean maternal age was 30.2 years at delivery, 51.5% were Hispanic, and 44.3% had an educational level equal to or above college level. PPD was reported in 10.5% of the study population, with higher rates seen in Black and non-Hispanic White patients, patients aged over 35 years, and patients with less than 4 years of college education.
All buffer sizes of green space exposures were associated with improvements in PPD, with a 500m buffer showing the most significant effects. An increase in street tree exposure was associated with a 2% decreased risk of PPD, while low-lying vegetation only decreased PPD risk in a 200m buffer of a patient’s residence or when found on grass within a 1000m buffer.
No association was found between PPD and NDVI, land-cover based green space, and park proximity. However, higher tree canopy cover was associated with lower PPD risk.
A positive association was also found between PA and most green space indicators. For every 10% increase in street tree within a 500m buffer, an associated 2.70% increase in PA during pregnancy was observed. However, more grasses exposures were associated with a decrease in PA during pregnancy.
Mediation effects from PA were measured from 2.7% to 7.2%. The largest mediation from PA was seen between street tree coverage and PPD. Overall, increased tree coverage saw the most significant effects on PPD rather than low-lying vegetation or grass.
Sun Y, Molitor J, Benmarhnia T, et al.Association between urban green space and postpartum depression, and the role of physical activity: a retrospective cohort study in Southern California. Lancet Reg Health Am. 2023;21.doi:10.1016/j.lana.2023.100462