Exploring Suicidal Ideation Predictors in U.S. Adults with Depression: The Roles of Demographics and Vitamin D in a Clinical Study

Objective Identifying predictors of suicidal ideation in adults with depression is crucial for developing preventive strategies. However, comprehensive studies that integrate demographic and vitamin D (VID) factors are limited. This study aimed to investigate potential predictors of suicidal ideation among U.S. adults with depression, with a particular focus on demographic and VID indicators. Additionally, a predictive model was developed via logistic regression combined with nomogram analysis. Methods A clinical prediction framework was developed utilizing multivariable logistic regression to assess the associations between suicidal ideation and variables such as sex, age, race, military service history, education level, marital status, household size, income‒poverty ratio, and VID concentrations (VD2 and VD3). The model's performance was assessed through receiver operating characteristic (ROC) curve analysis in both the training and validation cohorts. Results VID was significantly, albeit mildly, associated with suicidal ideation (OR 0.99, 95% CI 0.99–1.00; p = 0.033). In contrast, age and other demographic variables, including race, marital status, and household size, did not achieve statistical significance. Receiver operating characteristic (ROC) curve evaluation revealed moderate discriminative ability, with an area under the curve (AUC) of 0.636 (95% CI: 0.587–0.686) in the training cohort and 0.619 (95% CI: 0.517–0.720) in the validation cohort, suggesting acceptable generalizability. Conclusion VID concentrations may serve as a significant predictive factor for suicidal ideation among depressed adults in the United States, whereas demographic and socioeconomic factors exhibit limited predictive value.