Objective: Non-suicidal self-injury (NSSI) behaviors are prevalent in adolescents and have adverse effects on physical and mental health. However, little is known about the relationship between NSSI and alexithymia, or the underlying mechanisms that could explain this relationship. This study aimed to elucidate the current status of NSSI in adolescent depression, and analyze the relationship between alexithymia, loneliness, resilience, and adolescent depression with NSSI, so as to provide a theoretical basis for psychotherapeutic interventions. Method: The study sample involved inpatients and outpatients from 12 hospitals across China and adolescents with depression who met the DSM-5 diagnostic criteria for depression episode. The following scales were used: The Functional Assessment of Self-Mutilation, Toronto Alexithymia Scale, UCLA Loneliness Scale, and Connor Davidson Resilience Scale. Results: The detection rate of NSSI in adolescents with depression from 2021.01.01-2022.01.01 was 76.06% (1782/2343). Spearman’s correlation analysis revealed a significant correlation between alexithymia, loneliness, resilience and NSSI in depressed adolescents, and the results of the non-parametric test showed that the differences between the two groups for each factor were statistically significant. Binary logistic regression results showed that alexithymia (B = 0.023, p = 0.003, OR = 1.023, 95% CI: 1.008–1.038) and depression (B = 0.045, p < 0.001, OR = 1.046, 95% CI: 1.026–1.066) are risk factors for NSSI, resilience (B = − 0.052, p < 0.001, OR = 0.949, 95% CI: 0.935 − 0.964) is a protective factor for NSSI. Alexithymia directly predicted NSSI and also indirectly influenced NSSI through the mediated effect of resilience. Loneliness moderates the first half of the path of this mediated model. Conclusion: The present study confirms a moderated mediation effect: Alexithymia can have an impact on NSSI behaviors in depressed adolescents through the mediating role of resilience. Loneliness, as a moderating variable, moderated the first half of the pathway of the mediating model. We discuss perspectives for future research and interventions based on the findings of the study.

Objective: Non-suicidal self-injury (NSSI) behavior is very common in adolescents with depression, and childhood trauma is considered one of the distal risk factors for its exacerbation. Rumination caused by adverse traumatic experiences, which can be transferred through NSSI behavior, can alleviate symptoms of depression in adolescents. The current research focuses on the relationship between the three, further exploring whether rumination is a mediator in the relationship between childhood trauma and NSSI behavior on the basis of previous studies, and provides some suggestions for future early intervention for adolescents with depression. Methods: A total of 833 adolescent patients with depression who met the DSM-5 criteria for depressive episode were recruited from 12 hospitals in China. The Chinese version of the Function Assessment of Self-mutilation, Childhood Trauma Questionnaire, and Rumination Inventory were used as research tools. Results: The scores of childhood trauma and rumination in adolescents with depression in the NSSI group were higher than those in the non-NSSI group. A Pearson’s correlation analysis showed that childhood trauma was positively correlated with rumination (r=0.165, P< 0.01), different types of childhood trauma were significantly positively correlated with rumination and its three factors, and these results were statistically significant. Rumination partially mediated the relationship between childhood trauma and NSSI behavior in depressed adolescent patients (effect size=0.002), and the effect in female participants (effect size=0.003), was greater than that in male participants (effect size=0.002). Conclusion: Childhood trauma and rumination were key factors for NSSI behavior in adolescents with depression. Childhood trauma not only has a direct effect on NSSI behavior in adolescent depression, but also plays an indirect effect on NSSI behavior through rumination.