Parental depressive symptoms and shared reading practices among preschool children in western China: cross-sectional study.

Background: Shared reading supports early child development, but parental depressive symptoms may reduce its frequency and quality. Most previous studies assumed linear relationships with small samples. This large cross-sectional study examined linear and non-linear associations between parental depressive symptoms and shared reading practices in Chinese preschoolers. Methods: We recruited 21,366 parent-child dyads (children aged 3-6 years) from 189 kindergartens in western China. Depressive symptoms were measured with the Center for Epidemiologic Studies Depression Scale (CES-D). Shared reading was assessed using the StimQ READ subscale. Multivariable linear regression, piecewise linear regression with threshold estimation, and natural spline analysis were performed, adjusting for sociodemographic covariates. Results: Higher CES-D scores were linearly associated with lower total reading scores (adjusted β = -0.074 per point, 95% CI: -0.081 to -0.067). Piecewise regression identified a significant estimated breakpoint at CES-D score = 19.0 (95% CI: 11.9-26.1), below this threshold the slope was steeper (β = -0.085) than above (β = -0.051). Natural spline analysis confirmed non-linearity (P = 0.026) and located the point of maximum curvature at CES-D score = 10.9, indicating the most rapid change in slope occurred at subclinical symptom levels. The association was consistent across all subgroups (after Bonferroni correction). Conclusions: Parental depressive symptoms are negatively associated with shared reading in a non-linear, breakpoint-dependent manner. Even subclinical symptoms (CES-D score≈ 11) are associated with steeper declines, while the association attenuates at higher levels (CES-D score ≈ 19). Interventions targeting parental mental health, especially at subclinical to moderate symptom levels, may help preserve high-quality home literacy environments.