The Longitudinal Reciprocal Relations of Adolescents' Non‐Suicidal Self‐Injury and Suicidal Ideation and the Mediating Role of Irritability: A Random Intercept Cross‐Lagged Panel Model Analysis

BACKGROUND: In recent years, the prevalence of non-suicidal self-injury (NSSI) and suicidal ideation (SI) has been continuously increasing among adolescents, making it a global public health concern. While previous studies have identified a close relationship between NSSI and SI, few have delved into their reciprocal relationship and the underlying mechanisms. AIMS: This study aimed to examine the longitudinal relation between NSSI and SI, and the mediating role of irritability in the bidirectional association. MATERIALS AND METHODS: This study used the Brief Irritability Test (BIT), the Deliberate Self- Harm Inventory (DSHI), and the Beck Scale for Suicidal Ideation Chinese version (BSICV) in a three-wave longitudinal survey among 1711 Chinese adolescents (MAge = 14.44 years, SD = 1.35; 54.7% females), with 6-month intervals. Data were analyzed by using the random intercept cross-lagged panel model (RI-CLPM). RESULTS: The results revealed that: (1) At the between-person level, NSSI, irritability, and SI were all positively associated with one another. (2) Greater within-person NSSI predicted future greater SI and vice versa. (3) Greater within-person irritability predicted future greater SI and NSSI, and vice versa. (4) Irritability acted as a mediator in the bidirectional relations between NSSI and SI. DISCUSSION: The study proposed a dynamic and integrative perspective on the longitudinal relation among NSSI, irritability, and SI, emphasizing the evolving nature of these reciprocal relationships. CONCLUSION: These findings underscore the importance of addressing irritability in adolescents and highlight the need to enhance adolescents' emotional regulation skills to effectively mitigate the risk of NSSI and SI.