Association Between Household Income-Related Education and Postpartum Depression: A Two-Step Mendelian Randomization Study

Background: Previous research has demonstrated the associations between educational attainment, economic status, and postpartum depression (PPD). However, the associations between educational attainment, household income, and PPD based on Mendelian randomization (MR) have yet to be fully elucidated. Moreover, whether household income serves as a mediator in the association between education and PPD remains unclear. Methods: Using single-nucleotide polymorphisms (SNPs) extracted from genome-wide association studies (GWAS) as instrumental variables (IVs), we assessed the associations between education, household income, and PPD using MR analysis methods, such as inverse-variance weighting (IVW). The mediating effect was evaluated by examining (1) the association between education and household income and (2) the role of household income in the education—PPD relationship. Sensitivity analyses, including MR-Egger intercept analysis, leave-one-out analysis, Cochran’s Q test, and MR Pleiotropy RESidual Sum and Outlier (MR-PRESSO), were performed to assess robustness. Results: The MR analysis indicated that higher education (odds ratio (OR) = 0.877, 95% confidence interval (CI): 0.828–0.930; p = 1.050 × 10-5) and greater household income (OR = 0.443, 95% CI: 0.204–0.962; p = 0.040) were both associated with a reduced risk of PPD. Furthermore, we identified a significant association between education and household income (OR = 1.095, 95% CI: 1.085–1.105; p = 2.805 × 10-87). The mediation analysis demonstrated that household income partially mediated the relationship between education and PPD, with an indirect effect of –0.074 (95% CI: –0.146 to –0.004), accounting for 56.67% of the total effect. Conclusions: These findings suggest that household income significantly mediates the association between education and PPD. Moreover, higher education and increased household income can serve as important protective factors against PPD, underscoring the necessity for socioeconomic interventions aimed at reducing the risk of PPD.