Co-developmental trajectories of suicidal ideation and non-suicidal self-injury among Chinese adolescents: Transdiagnostic predictors and association with suicide attempts

Introduction Adolescent suicidal ideation (SI) and non-suicidal self-injury (NSSI) are crucial public health issues, yet their co-developmental trajectories during early adolescence and their associations with predictors and outcomes are unclear. This study aimed to (a) identify heterogeneous co-developmental trajectories of SI and NSSI, (b) explore associations between transdiagnostic predictors and trajectories, and (c) assess suicide attempt risk across trajectories. Methods Four hundred fifty-three adolescents (Mage = 12.35 years, 48.3% boys) completed surveys at 6-month intervals across 2 years. At Time 1 (Nov 2020), participants completed surveys encompassing SI, and NSSI, along with family, peer, and individual predictors. Subsequent surveys (Times 2–4) measured SI and NSSI, with suicide attempts queried at Time 4. Results Parallel process latent class growth models revealed three co-developmental groups (i.e., Stable low NSSI and SI; Moderate-NSSI and high-SI, parallel decreasing; High-NSSI and moderate-SI, parallel increasing). Multivariate logistic regression indicated that group membership was predicted by parental rejection, parental warmth, bullying victimization, depressive and anxiety symptoms, thwarted belongingness, and perceived burdensomeness. Adolescents in the “High-NSSI and moderate-SI, parallel increasing” group reported the highest suicide attempt frequency. Conclusion These findings underscore subgroup distinctions and transdiagnostic predictors in comprehending SI and NSSI progression, emphasizing the necessity of dynamic monitoring and tailored interventions for distinct subgroup characteristics.