Major depressive disorder (MDD) is one of the most prevalent medical conditions worldwide. Different factors were found to play a role in its etiology, including environmental ones (e.g., air pollution). The aim of this study was to evaluate the association between air pollution exposure and MDD severity.

Four hundred sixteen MDD subjects were recruited. Severity of MDD and functioning were evaluated through five rating scales: Montgomery–Asberg Depression Rating Scale (MADRS), Hamilton Depression Rating Scale (HAMD), Clinical Global Impression (CGI), Global Assessment of Functioning (GAF), and Sheehan Disability Scale (SDS). Daily mean estimates of particulate matter with diameter ≤10 (PM10) and 2.5 μm (PM2.5), nitrogen dioxide (NO2), and apparent temperature (AT) were estimated based on subjects’ residential addresses. Daily estimates of the 2 weeks preceding recruitment were averaged to obtain cumulative exposure. Multivariate linear and ordinal regression models were applied to assess the associations between air pollutants and MDD severity, overall and stratifying by hypersusceptibility and AT.

Two-thirds of subjects were women and one-third had a family history of depression. Most women had depression with symptoms of anxiety, while men had predominantly melancholic depression. NO2 exposure was associated with worsening of MDD severity (HAMD: β = 1.94, 95% confidence interval [CI], [0.41–3.47]; GAF: β = −1.93, 95% CI [−3.89 to 0.02]), especially when temperatures were low or among hypersusceptible subjects. PM exposure showed an association with MDD severity only in these subgroups.

Exposure to air pollution worsens MDD severity, with hypersusceptibility and lower temperatures being exacerbating factors.

Breast milk is a dynamic type of nourishment that changes based on the needs of the child. An increasing amount of data suggests that mental health may be an important factor in such modulation. In addition, breast milk contains extracellular vesicles (EVs), which are currently considered an important dynamic system of communication between cells, even of different individuals.

Purpose of this article is to investigate whether changes in breast milk in terms of EVs concentrations are related to maternal mental health.

This is a case-control study for which we enrolled mothers of infants with bronchiolitis (N=33) and mothers of healthy infants (N=13). Breast milk samples were taken and EVs concentrations were quantified. Maternal mental health was assessed by administration of five different psychometric scales: Edinburgh Postnatal Depression Scale (EPDS), State Trait Anxiety Inventory (STAI-S, STAI-T), Barkin Index of Maternal Functioning (BIMF), The Connor-Davidson Resilience Scale 10 items (CD-RISC). Subsequently, scale scores were related to evs concentrations by negative binomial regressions adjusted for case-control.

As maternal resilience increases, the EVs of neutrophilic origin (p=0.0447) and those of endothelial origin (p=0.0078) decrease¹. In contrast, an increased EPDS score is associated with higher levels of B-lymphocyte EVs (p=0.0376). Scores on the STAI-S scale impact many more populations of EVs²: we observed an increased Incidence Rate Ratio (IRR) of neutrophil-derived EVs (p<0.0001), T-lymphocyte- derived EVs (p=0.0214), NK-cell-derived EVs (p=0.0202), T-reg CD4+ CD25+ (p=0.0141) and endothelial marked EVs (p=0.0180). An increase in STAI-T scale scores also was associated with a significant increase in CD177+ neutrophil-derived EVs (p=0.0028) and endothelial-derived EVs (p=0.0111)³.

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EVs concentrations in breast milk are associated with maternal mental health. Specifically, stress and related severity of anxiety is able to increase the concentrations of EVs derived from inflammatory cells, which suggests an increase in their number and activity. Further research is needed to confirm these preliminary findings.

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