Association between parity and female depression: the mediative role of sleep duration.

BACKGROUND: This cross-sectional study aimed to investigate whether parity is associated with depressive symptoms among women, and whether sleep duration mediates this association. METHODS: Our analytical sample comprised 14,493 female participants drawn from six consecutive NHANES cycles (2007–2018). Parity status was ascertained through structured self-administered questionnaires, while depressive symptoms were quantified using the validated nine-item Patient Health Questionnaire (PHQ-9) with a standardized cutoff score ≥ 10 indicating clinically significant symptoms. We employed multivariable-adjusted logistic regression models to evaluate the parity-depression association, complemented by restricted cubic spline (RCS) regression to assess non-linear dose-response relationships. A mediation analysis framework was implemented to quantify sleep duration’s potential intermediary role, supported by multiple sensitivity analyses to verify result robustness. RESULTS: The analysis revealed a non-linear dose-response relationship (inverted L-shape) between parity and depressive symptoms. Compared to nulliparous women after full covariate adjustment, primiparous and multiparous women demonstrated significantly elevated risks: those with 1–3 live births showed a 46% increased risk (Odds Ratio (OR) = 1.46, 95%CI 1.17–1.82, p = 0.001), while women with ≥ 4 births exhibited a 63% higher risk (OR = 1.63, 95%CI 1.26–2.11, p < 0.001). The subgroup analyses identified significant effect modification by both age category (p-interaction = 0.002) and race (p-interaction = 0.03).Mediation models estimated that sleep duration accounted for 12.86% of the total parity-depression association. CONCLUSION: There is a non-linear, dose-dependent association between parity and depressive symptoms, and sleep duration was identified as a partial statistical mediator. These findings underscore the need for integrating parity assessment and perinatal sleep management into depression prevention strategies.