Trait, state, and behavior in adolescent NSSI addiction: a serial mediation model linking childhood trauma to NSSI addiction

Abstract

Despite growing recognition of non-suicidal self-injury (NSSI) as a potential behavioral addiction, the sequential mechanisms linking childhood trauma to NSSI addiction remain unclear. This study examined a serial mediation model testing whether trait impulsivity and depressive symptoms sequentially mediate this relationship, with NSSI function as a behavioral coping mechanism. This cross-sectional study included 163 Chinese adolescents diagnosed with major depressive disorder and a history of NSSI. Participants completed the Childhood Trauma Questionnaire-Short Form, the Short UPPS-P Impulsive Behavior Scale, the Children’s Depression Inventory, and the Ottawa Self-Injury Inventory (Functions and Addictive Features subscales). Serial mediation analysis (PROCESS Model 6, 5,000 bootstrap resamples), controlling for demographic and clinical covariates, tested the hypothesized five-step sequential model. Childhood trauma was positively associated with NSSI addiction, and this association was predominantly mediated: the total indirect effect accounted for 56.2% of the total effect. Indirect effects involving NSSI function in combination with upstream mediators were significant, including the full sequential path (B = 0.0033, 95% CI [0.0007, 0.0083]), whereas simple mediations via impulsivity, depression, or NSSI function alone were not. These findings support a trait-state-behavior-addiction cascade in which childhood trauma is associated with trait impulsivity and depressive symptoms that, in combination with the reinforcing function of NSSI, are linked to addictive features of NSSI. The model advances theoretical understanding of NSSI addiction and offers actionable clinical targets for prevention and intervention. Longitudinal studies are needed to confirm causal directions.