Jiaqi Zhou,1 Shiyi Hu,1 Haoze Wu,1 Suhong Wang,2 Jingbo Gong3 

1Shanghai Key Laboratory of Mental Health and Psychological Crisis, Affiliated Mental Health Center (ECNU), School of Psychology and Cognitive Science, East China Normal University, Shanghai, People’s Republic of China; 2Department of Clinical Psychology, The Third Affiliated Hospital, Soochow University, Changzhou, People’s Republic of China; 3Shanghai Changning Mental Health Center, Affiliated Mental Health Center of East China Normal University, Shanghai, People’s Republic of China

Correspondence: Jingbo Gong, Shanghai Changning Mental Health Center, Affiliated Mental Health Center of East China Normal University, 299 Xiehe Road, Changning District, Shanghai, 200335, People’s Republic of China, Email yefenhua@126.com Suhong Wang, Department of Clinical Psychology, The Third Affiliated Hospital, Soochow University, Changzhou, People’s Republic of China, Email yarmine@gmail.com

Introduction: Non-suicidal self-injury (NSSI) is a prevalent issue among adolescents, with potential long-term mental health implications. To investigate NSSI thoughts as a distinct developmental stage and inform early intervention strategies, this study employed a longitudinal design to examine progression differences in Chinese adolescents across three NSSI status: NO NSSI, NSSI thoughts without behaviors, and NSSI behaviors.
Methods: Using a machine learning approach (Random Forest models), a two-wave longitudinal study assessed 2,154 adolescents (aged 11– 18) from Chinese middle and high schools. Analyses focused on NSSI status, risk factors, and developmental trajectories. ANOVAs and paired-t tests were conducted to examine risk factors and NSSI functions of group with different NSSI status.
Results: NSSI thoughts emerged as both a distinct category and a potential precursor to behaviors. Despite limitations in accurately classifying the NSSI thoughts group, the Random Forest models demonstrated capability in differentiating NSSI status. Age-specific patterns were identified: middle school students showed a higher propensity to progress to NSSI behaviors than high schoolers, with emotional/social factors more prominent for middle schoolers and broader risk factors for high schoolers.
Conclusion: Findings support conceptualizing NSSI thoughts as a critical stage in NSSI development, highlighting distinct risk profiles across age groups. Future research should focus on improving the identification and assessment of NSSI thoughts and developing early intervention strategies based on developmental stages and associated risk factors.

Keywords: non-suicidal self-injury, adolescence, random forest models