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en Machine Learning Classification of Lifetime Suicide Attempts Among Iranian Military Conscripts: A Gradient Boosting Approach Aims: This study evaluated the utility of machine learning, specifically a Gradient Boosting model (GBM), in classifying lifetime suicide attempts among Iranian military conscripts to overcome the limitations of traditional linear assessments. Methods: In a cross-sectional study of 338 conscripts, psychological data were collected using the Beck Hopelessness Scale–Short Form, Suicide Capacity Scale–Version 3, Psychache Scale, Acquired Capability for Suicide Scale–Fearlessness About Death (ACSS-FAD), Suicidal Behaviors Questionnaire-Revised (SBQ-R), and Interpersonal Needs Questionnaire. A GBM was trained to classify participants based on lifetime suicide attempt history and benchmarked against Logistic Regression. Feature importance was interpreted using SHapley Additive exPlanations (SHAP) to ensure clinical transparency. Findings: The GBM achieved high classification accuracy (AUC = 0.9344), outperforming the Logistic Regression model (AUC = 0.9180). SHAP analysis identified the ACSS-FAD and SBQ-R as the most significant features distinguishing attempters from non-attempters. Furthermore, intense psychological pain (Psychache) emerged as a key discriminative factor in identifying the high-risk group. The GBM effectively captured complex, non-linear risk patterns. Conclusion: "Capacity" factors are central to the psychological profile of attempters. Integrating non-linear machine learning techniques with theory-driven tools like the ACSS-FAD provides a robust, data-driven approach for accurately distinguishing high-risk individuals and tailoring targeted military suicide prevention strategies.   1001 1010 http://ijwph.daneshafarand.org/browse.php?a_code=A-10-1-125&slc_lang=en&sid=3 N. Goodarzi 1003194753284600387874 1003194753284600387874 No M. Imani 1003194753284600387875 1003194753284600387875 No H. Mohsenabadi 1003194753284600387876 1003194753284600387876 No M.J. Shabani shabani.mjavad@gmail.com 1003194753284600387877 1003194753284600387877 Yes