Exposure to urban environmental stressors in pregnancy and postpartum depression: A meta-analysis of 11 European birth cohorts

Background and Aim: Urban environmental stressors have been associated with adult depression, but few studies on postpartum depression (PPD) exist. We investigated associations between exposure to urban environmental stressors in pregnancy and PPD. Methods: We included women from 11 European birth cohorts within the EU Child Cohort Network with singleton pregnancies between 1990-2016 and no previously reported depression. Exposures included ambient air pollution (NO2, PM2.5 and PM10), road traffic noise, natural spaces (Normalised Difference Vegetation Index; NDVI, access to major green and blue spaces) and built environment (population density, facility richness and walkability). PPD was assessed using self-report questionnaires collected 3 – 18 months after birth (e.g. Edinburgh Postnatal Depression Questionnaire). We used adjusted logistic regression to estimate cohort-specific associations between single exposures and PPD and pooled results via meta-analysis using DataSHIELD. We also fit multiple exposure models where we hypothesised one exposure may confound the relationship between another exposure and PPD. Results: Rates of PPD ranged from 2 – 17% across cohorts (n = 39,329). In the pooled sample higher levels of NDVI were associated with reduced odds of PPD (OR per IQR difference in NDVI = 0.94, CI 0.89, 1.00), although results were not consistent across indicators of green spaces. We also found a trend for higher levels of traffic noise to be associated with increased odds of PPD (OR Lden >70dB = 1.19, CI 0.89, 1.59). For all other urban stressors associations were close to null and there was considerable heterogeneity between cohorts. Multiple exposure models showed similar results. Conclusions: Overall, this large European meta-analysis provides little evidence for an association between urban environmental stressors and PPD, although our findings provide some evidence that lack of green spaces may be associated with greater risk of PPD. Key words: post-partum depression, air pollution, natural spaces, traffic noise