Adverse Childhood Experience, Loneliness, and Adolescent Non-Suicidal Self-Injury: A Moderated Mediation Analysis of Gender Differences

Background: Non-suicidal self-injury (NSSI) is a significant public health concern among adolescents, with adverse childhood experiences (ACEs) as robust predictors. However, the psychological mechanisms linking ACEs to NSSI remain inadequately understood, particularly regarding whether specific ACE subtypes operate through distinct pathways and whether these pathways differ by gender. Loneliness has been proposed as a mechanism through which childhood adversity generates self-injurious behavior, yet no prior study has examined this pathway at the level of ACE subtype specificity with gender moderation simultaneously. This study examined the mediating role of loneliness in the ACE–NSSI relationship among Chinese adolescents, testing whether effects differ by ACE subtype and gender.

Methods: A cross-sectional cluster sampling design was employed with 993 high school students (67.6% female, 32.4% male; mean age not reported) recruited from an art preparatory academy in China between March and May 2024. ACEs were measured using the ACE-Q, loneliness using the UCLA Loneliness Scale, and NSSI using the DSHI-9r. Structural equation modeling with bias-corrected bootstrap confidence intervals examined both mediation and moderated mediation effects across ACE subtypes.

Results: NSSI prevalence was 17.2%. Loneliness significantly mediated the ACE–NSSI relationship, but exclusively for emotional maltreatment (β = 0.021, 95% CI [0.009, 0.040]); no significant indirect effect emerged for other ACE subtypes regardless of gender. Gender moderation was also specific to emotional maltreatment: females demonstrated a significantly stronger indirect effect (β = 0.025) than males (β = 0.014), with the difference statistically significant (β = −0.123, 95% CI [−0.233, −0.019]). Among males and for all other ACE subtypes, indirect effects through loneliness were non-significant.

Conclusions and Implications: These findings indicate that ACE subtypes operate through distinct psychological mechanisms, and that loneliness reduction is a specifically warranted intervention target for female adolescents with emotional maltreatment histories — not for ACE-exposed youth as an undifferentiated group. School social workers conducting trauma screening should supplement universal ACE checklists with subtype-specific assessment that distinguishes emotional maltreatment from other adverse experiences. For female students identified with emotional maltreatment histories, social workers should prioritize peer support programming and group-based social connectedness interventions as proximal strategies for NSSI prevention. These findings also suggest that gender-neutral, generalized trauma-informed approaches may be insufficient; gender-stratified risk assessment protocols should be incorporated into school mental health frameworks.