Background: Up to 60% of US populations live in proximity to high-volume roadways with potential exposure to hazardous traffic-related air pollution (TRAP). Studies show exposure to TRAP has deleterious effects on mental health. However, little is known about the extent to which such linkages are attributable to explanatory factors (demographics, socioeconomic status (SES), and general/reproductive health), which may enhance understanding of the pathways through which TRAP confers risk.

Objective: To both examine the effects of TRAP on depressive symptoms, accounting for explanatory factors, and explore whether reproductive health indicators mediate effects of TRAP on depressive symptoms.

Methods: Participants were 688 healthy, premenopausal women in the Ovarian Aging Study. TRAP was derived from distance-weighted traffic counts using residential addresses. Depressive symptoms were assessed by self-report on the Center for Epidemiological Studies Depression (CESD) scale. Explanatory factors were assessed by interview and clinical assessments.

Results: In cross-sectional, multivariate analyses, greater exposure to TRAP was related to more depressive symptoms (b=.779, p=.015). A one-SD increase in TRAP was associated with a 0.8-point mean increase on the CESD scale. Variance in depressive symptoms was attributable to TRAP (1.2%, p=.004), demographics (1.0%, p=.217), SES (1.4%, p=.007), general health (0.3%, p=.356), and reproductive health (2.0%, p=.015). The reproductive health indicator, menstrual cycle length, partially mediated effects of TRAP on depressive symptoms (indirect effect: b=.101, p=.008).

Discussion: Findings suggest exposure to TRAP may confer risk for depression, along with SES and reproductive health indicators, and that reproductive health may be a pathway through which TRAP impacts depression.