| Background Suicidal ideation serves as a sensitive predictive indicator for non-suicidal self-injury, and the impact of non-suicidal self-injury on the psychophysical well-being of high school students is substantial. Existing research has separately explored the associations between insomnia, anxiety, and non-suicidal self-injury in the general population. However, the internal mechanisms underlying non-suicidal self-injury among high school students with suicidal ideation remain to be investigated. Objective To explore the relationship among insomnia, anxiety and non-suicidal self-injury, providing an evidence for psychological intervention in non-suicidal self-injury among high school students. Methods Using a cluster-randomized sampling approach, 2421 high school students from three high schools in Hubei Province, China, were selected. The Insomnia Severity Index Questionnaire (ISI), 7-items Generalized Anxiety Disorder Scale (GAD-7), and Adolescents Self-Harm Scale (ASHS) were administered for assessment. Spearman’s correlation analysis was conducted to examine the correlations, and Model 4 from the SPSS Process 4.2 was employed to test the mediating role of anxiety between insomnia and non-suicidal self-injury. Results In this study, there were 554 high school students with suicidal ideation (22.88%) and 1867 students without suicidal ideation (77.12%). The ISI scores, GAD-7 scores, and ASHS scores of high school students with suicidal ideation were all higher than those without suicidal ideation (p<0.01). Spearman’s correlation results indicate a positive correlation between ISI scores and GAD-7 scores among high school students with suicidal ideation (r=0.646, P＜0.01). Additionally, a positive correlation is observed between ISI scores and NSSI scores (r=0.354, P＜0.01), as well as between GAD-7 scores and NSSI scores (r=0.375, P＜0.01) in this population. Anxiety mediated between insomnia and non-suicidal self-injury of high school students with suicide ideation (ab=0. 111，95% CI：0.053~0. 185) and the ratio of intermediation effect to total effects was 53.88%. Conclusion The insomnia among high school students with suicidal ideation can directly influence non-suicidal self-injury and also exert an indirect impact on non-suicidal self-injury through anxiety. |