Abstract / Summary
Abstract Background Disordered lipid metabolism is a significant physical risk factor in the pathophysiological mechanisms underlying adolescent depressive disorders. The non-HDL-c to HDL-c ratio (NHHR) comprehensively reflects the degree of lipid imbalance. Previous studies have confirmed a linear association between lipid profile parameters and the risk of depression or suicide. However, the nonlinear relationship between the NHHR and suicidal ideation in adolescents with depressive disorders remains unclear—and whether a dose-response relationship exists between these two variables awaits clinical validation. Based on this background, our study focused on adolescents with depressive disorders and investigated the association pattern between the NHHR and suicidal ideation. We found that there is a ‘U’-shaped nonlinear relationship between them, and identified a critical threshold value of the NHHR that influences the risk of suicidal ideation. Moreover, we determined the risk characteristics of suicidal ideation corresponding to both high and low levels of lipid metabolism. The objectives of this study were to refine the theoretical framework regarding lipid metabolism-related mechanisms underlying suicide risk in adolescents with depressive disorder and to provide an evidence-based reference for early screening and individualized intervention for suicidal ideation in this population. Methods This cross-sectional study was conducted at Wutai Mountain Hospital in Yangzhou, Jiangsu Province, China, from January to June 2026, enrolling 291 adolescents with depressive disorders. Logistic regression was employed to assess the relationship between the NHHR and suicidal ideation, while a binary linear regression model was used to analyze the threshold effect. Results After accounting for the potential influence of confounding variables, binary logistic regression analysis yielded results indicating that there was no statistically significant association between the NHHR and suicidal ideation ( p > 0.05). However, visual analysis of the smoothed curve revealed a ‘U’-shaped relationship among these three variables and depressive symptoms, with the inflection point occurring at an NHHR index value of approximately 2.63. The effect sizes and their 95% confidence intervals on both sides of the inflection point were observed as follows: (95% CI: 0.017 to 0.453, p = 0.035) and − 0.297 (95% CI: −0.567 to − 0.027, p = 0.032). Conclusion Among adolescents with depressive disorder, a ‘U’-shaped association was observed between the NHHR index and suicidal ideation: when the NHHR index reaches 2.63, the risk of suicidal ideation is at its highest, suggesting that an increased risk of suicidal ideation may be associated with either lower or higher levels of the NHHR index.