Alexithymia and self-injury functions as mediators between childhood maltreatment and nonsuicidal self-injury in adolescents with major depressive disorder.

Childhood Maltreatment (CM) is a critical risk factor for non-suicidal self-injury (NSSI) and major depressive disorder (MDD). However, the mechanisms by which CM influences NSSI through alexithymia and self-injury functions (SF) remain unclear. This study aims to investigate the mediating roles of alexithymia and SF in the relationship between CM and NSSI and to explore the interrelations among these variables in adolescents with MDD. The study sample included 260 MDD patients and 125 healthy controls, with a mean age of 15.10 ± 1.74 years and 230 females (62.5%), and after propensity score matching (PSM), 166 MDD patients and 101 healthy controls were included in the final analysis. The primary variables examined were alexithymia, CM, self-injurious behaviors, and SF. Structural equation modeling (SEM) was employed to evaluate the direct effect of CM on NSSI, as well as the mediating effects of alexithymia and SF. The prevalence of NSSI (65.1%), CM (78.3%), and alexithymia (77.1%) in MDD patients were significantly higher than in the control group, where the rates were 7.9%, 35.6%, and 41.6%, respectively (P < 0.001). The most common methods among MDD patients were cutting the skin (59.63%), pinching body parts until bleeding (60.24%), and inserting objects under the skin or nails (56.63%). SEM revealed that CM was directly associated with difficulty identifying feelings (DIF) (β = 0.439, P < 0.001) and depressive symptoms (β = 0.418, P < 0.001). Similarly, SF was strongly correlated with NSSI (β = 0.575, P < 0.001). However, there was no direct effect of CM on SF (β = 0.138, P = 0.171), nor of DIF on NSSI (β = -0.114, P = 0.115). Finally, CM had a significant direct effect on NSSI (β = 0.346, P < 0.001) and an indirect effect on NSSI through DIF and SF (β = 0.072, P = 0.022). This study demonstrates that difficulty identifying feelings and self-injury functions partially mediated the relationship between CM and NSSI. These findings highlight the importance of targeting key symptom nodes, specifically difficulty identifying feelings and self-injury functions, in interventions and treatment efforts for NSSI.