Abstract
Suicidal ideation is a major public health concern in mood disorders. We examined whether disturbances across multiple biological rhythm domains are associated with suicidal ideation during depressive episodes. In a cross-sectional study, 287 adults with major depressive disorder or bipolar disorder were recruited from three hospitals in China (2023-2024). Suicidal ideation was defined using Patient Health Questionnaire-9 item 9; biological rhythms were assessed with the Chinese version of the Biological Rhythms Interview of Assessment in Neuropsychiatry; anxiety was measured with the Generalized Anxiety Disorder-7. In multivariable logistic regression, greater depressive symptom severity, more severe sleep and eating rhythm disruption, and earlier age at first depressive episode were independently associated with suicidal ideation. Model performance was acceptable (Nagelkerke R² = 0.585; Hosmer-Lemeshow p = 0.69). Receiver operating characteristic analyses yielded clinically relevant thresholds (area under the curve: PHQ-9, 0.870 with cutoff 15; sleep rhythm, 0.851 with cutoff 11; eating rhythm, 0.814 with cutoff 9; age of onset, 0.719 with cutoff 23 years). Overall, 69.7% of participants endorsed suicidal ideation. These findings suggest that incorporating biological rhythm assessment with depressive symptom evaluation may improve identification of individuals at elevated risk. Longitudinal studies are needed to clarify mechanisms and guide prevention.