Table 2 shows the results of the modified Poisson regression analysis in the overall population. We did not observe significant associations between prenatal depression and childhood respiratory outcomes. Postpartum depression was significantly associated with increased risk of current wheeze (RR: 1.88, 95% CI: 1.21, 2.92) and asthma (RR: 2.79, 95% CI: 1.13, 6.87) at 48 months. We observed an association between postpartum depression and any current wheeze (RR: 1.59, 95% CI: 1.03, 2.46) and ever asthma (RR: 2.15, 95% CI: 1.06, 4.39). Lastly, a statistically significant association was observed between postpartum depression and ever wheeze at 72 months (RR: 1.54, 95% CI: 1.02, 2.32).

Maternal recurrent depression was associated with an increased risk of ever wheeze at 48 months (RR: 1.48, 95% CI: 1.07, 2.03) and 72 months (RR: 1.76, 95% CI: 1.12, 2.77). It was also associated with increased risks of current wheeze (RR: 2.39, 95% CI: 1.52, 3.78) and asthma at 48 months (RR: 3.14, 95% CI: 1.26, 7.84). Additionally, we found that recurrent depression was associated with increased risks of any ever wheeze (RR: 1.53, 95% CI: 1.15, 2.03), any current wheeze (RR: 2.08, 95% CI: 1.32, 3.28), and ever asthma (RR: 2.46, 95% CI: 1.16, 5.21).

In two-way interaction models, we found evidence for effect modification by sex for postpartum (p_interaction= 0.06) and recurrent depression (p_interaction= 0.06) on current wheeze at 48 months. As shown in figure 1, postpartum depression were associated with higher risk of current wheeze at 48 months in females (RR: 3.04, 95% CI: 1.47, 6.27) when compared to males (RR: 1.53, 95% CI: 0.87, 2.68). We observed a similar pattern for recurrent depression, with females having a higher risk of current wheeze (RR: 3.95, 95% CI: 1.86, 8.36) when compared to males (RR: 1.92, 95% CI: 1.06, 3.46). We also found interactions between child sex and postpartum depression (p_interaction= 0.05) on current wheeze at 72 months (figure 2). Sensitivity analyses including additional adjustment for average PM_2.5 in the first 2 postnatal years, breastfeeding, and SES showed similar results (results not shown).