Yigao Wu,1,2,* Wenhao Jiang,1,* Man Chen,2 Qin Jiang,2 Huilan Huang,2 Wenbin Guo,3 Yonggui Yuan1 

1Department of Psychiatry and Psychosomatics, Zhongda Hospital, School of Medicine, Jiangsu Provincial Key Laboratory of Brain Science and Medicine, Southeast University, Nanjing, People’s Republic of China; 2Department of Medical Psychology, The First Affiliated Hospital of Wannan Medical College, Wuhu, People’s Republic of China; 3Department of Psychiatry, National Clinical Research Center for Mental Disorders, and National Center for Mental Disorders, The Second Xiangya Hospital of Central South University, Changsha, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Yonggui Yuan, Department of Psychiatry and Psychosomatics, ZhongDa Hospital, School of Medicine, Jiangsu Provincial Key Laboratory of Brain Science and Medicine, Southeast University, No. 87 Dingjiaqiao, Gulou District, Nanjing, 210009, People’s Republic of China, Tel +86-025-83285124, Email yygylh2000@sina.com

Objective: To examine the relationship between the systemic immune inflammatory index (SII) and suicide attempts (SA) in individuals experiencing their first episode of major depressive disorder (MDD).
Methods: A retrospective analysis of 338 MDD patients (2020– 2023) at the First Affiliated Hospital of Wannan Medical College and 76 healthy controls (HC) was conducted. MDD patients were categorized based on their history of SA. Differences in SII and clinical characteristics were analyzed, and a receiver operating characteristic (ROC) curve was used to determine the optimal SII cutoff for predicting SA. Binary logistic regression identified independent risk factors associated with SA.
Results: MDD patients exhibited higher levels of neutrophils, platelets, and SII compared to HC (all p< 0.05). SA Patients had higher HDRS scores, neutrophil counts, mean platelet counts, and SII values compared to those without SA (all p< 0.05). ROC analysis identified an optimal SII cutoff of 515.3, with 67% sensitivity, 70% specificity, and an area under the curve (AUC) of 0.692. After adjusting for gender, age, body mass index, disease duration, and quality of life, individuals with elevated SII values were 8.318 times more likely to have recent SA (OR=8.318, 95% CI: 3.767– 17.546, p< 0.05). Patients with high SII values were 14.101 times more likely to have recent SA compared to those with low SII values (OR=14.101, 95% CI: 5.356– 34.235, p< 0.05). However, high SII was not identified as a significant risk factor for previous SA (OR=0.607, 95% CI: 0.061– 4.961, p> 0.05).
Conclusion: SII represents a cost-effective and accessible method for evaluating suicide risk in patients with MDD.

Keywords: systemic immune inflammatory index, first-episode, major depressive disorder, suicide attempts, immune