Objective <p>This study aims to investigate the factors influencing suicidal ideation in patients with bipolar depressive disorder (BDD), focusing primarily on cognitive function, brain-derived neurotrophic factor (BDNF), sleep quality, and depressive symptoms.</p> Methods <p>A total of 126 patients with depressive episodes of bipolar disorder and 38 healthy controls were recruited for this study. Participants were divided into suicidal ideation and non-suicidal ideation groups based on the Beck Scale for Suicide Ideation-Chinese Version (BSI-CV). Depressive symptoms were assessed using the 24-item Hamilton Rating Scale for Depression (HAMD-24), and sleep quality was evaluated using the Pittsburgh Sleep Quality Index (PSQI). Cognitive function was measured using the Chinese version of the MATRICS Consensus Cognitive Battery (MCCB), and serum BDNF levels were determined.</p> Results <p>24.6% of the patients exhibited suicidal ideation. High depression scores and poor sleep quality were identified as risk factors, whereas good cognitive function and higher levels of BDNF served as protective factors. Receiver Operating Characteristic (ROC) analysis revealed that serum BDNF, depressive symptoms, sleep quality, and cognitive function have significant predictive value, with a combined use of these four indicators yielding even better predictive results.</p> Conclusion <p>Serum BDNF levels, depression scores, sleep quality scores, and cognitive function scores can be used as predictive indicators for suicidal ideation in BDD patients. The combined use of these four indicators provides optimal predictive efficacy.</p>