Objective
Non-suicidal self-injury (NSSI) refers to the behavior in which an individual injures his or her own body in a deliberate, self-directed, and non-culturally sanctioned manner without suicidal intent and has a high prevalence among adolescents. Adolescence is a critical time for relationship needs to be satisfied, and adolescents are more likely to experience psychological distress such as depression and anxiety, thus increasing the risk of NSSI. The functional theory of non-suicidal self-injury suggests that adolescents will engage in NSSI as a way to meet their relatedness needs (Nock, 2010); the experiential avoidance theory of non-suicidal self-injury suggests that adolescents will exacerbate psychological distress by engaging in NSSI as a way to avoid it (Chapman et al., 2006). However, previous cross-sectional-based studies have been unable to examine the causality of NSSI in adolescents, and longitudinal-based studies have lacked the ability to examine the post-NSSI consequences. Therefore, the purpose of this study was to examine whether there is a longitudinal interplay between relatedness need satisfaction and NSSI, and psychological distress and NSSI, and to examine the longitudinal relationship between relatedness need satisfaction, psychological distress, and NSSI.
Methods
A six-month follow-up study of 475 adolescents from Zhejiang Province was conducted using cluster sampling to collect three waves of data using the Self-Injury Functional Assessment Scale (SIFAS), the Basic Psychological Needs Satisfaction Scale (BPNSS), and the Depression and Anxiety Stress Scale (DAS). Cross-lagged modeling was used to analyze the longitudinal relationships among adolescents' NSSI, relatedness needs satisfaction, and psychological distress.
Results & Discussion
(1) There is a bidirectional negative relationship between T1-T2 relationship need satisfaction and self-injury. (2) There was a bidirectional positive predictive relationship between T1-T2 psychological distress and self-injury. (3) There was a partial intertemporal mediating effect of T2 psychological distress between T1 self-injury and T3 relatedness need satisfaction. (4) There was a cyclical effect between T1-T3 relationship need satisfaction and psychological distress and self-injury. Adolescents with unsatisfied relationship needs are at increased risk for subsequent NSSI, and adolescents who engage in NSSI may be isolated from others and have unsatisfied relationship needs; psychological distress contributes to adolescent NSSI, and engaging in NSSI reduces adolescents' distress tolerance and increases psychological distress; adolescent NSSI exacerbates adolescent psychological distress and leaves subsequent relationship needs unsatisfied; adolescents who engage in NSSI because of psychological distress exacerbate psychological distress; and adolescents who engage in NSSI because of unsatisfied relationship needs have relationship needs satisfied.
Conclusions
The bidirectional relationships between adolescents' relatedness need satisfaction and NSSI, psychological distress and NSSI are lagged and have a "snowball" cyclical relationship; adolescents' NSSI increases subsequent psychological distress, which indirectly leads to unsatisfied relatedness needs. The present study supports the functional theory of non-suicidal self-injury and the experiential avoidance theory, which have important implications for the intervention of adolescent NSSI.
Acknowledgement: This research was supported by the Zhejiang Educational Science Planning Project (No.2024SCG358), Zhejiang Province Philosophy and Social Science Planning Project (No.24NDQN22Z).
References:
Chapman, A. L., Gratz, K. L., & Brown, M. Z. (2006). Solving the puzzle of deliberate self-harm: The experiential avoidance model. Behaviour Research and Therapy, 44(3), 371-394. https://doi.org/10.1016/j.brat.2005.03.005 
Nock, M. K. (2010). Self-injury. Annual Review of Clinical Psychology, 6(1), 339-363. https://doi.org/10.1146/annurev.clinpsy.121208.131258 

adolescent,non-suicidal self-injury,relatedness need satisfaction,psychological distress,cross-lagged model,bidirectional association