Developmental Trajectories of Self-, Other-, and Dual-Harm across Adolescence: The Role of Relationships with Peers and Teachers.

Introduction: We investigated the longitudinal course of self-, other-, and dual-harm in adolescents, focusing on the infliction of physical injury on oneself, another person, or both parties, respectively. We examined the within-person transitions between these types of harm and whether relationships with peers and teachers predict individual harm trajectories.

Methods: We used community-representative longitudinal data (N = 1,482; 52% male; 50% both parents born abroad). The participants self-reported self- and other-harm at 13, 15, 17, and 20 years. We assigned them to groups with self-, other-, dual- or no harm at specific assessments. Bullying victimization and relationship quality with classmates and teachers were assessed at 13 and 17. We estimated transition probabilities between the harm groups using latent Markov chain models.

Results: At age 13, 3% of the sample engaged in dual-harm, 10% in self-harm only, and 7% in other-harm only. These percentages decreased in late adolescence. Initial dual-harm was often followed by sex-specific single-harm: most of the female participants transitioned to self-harm, and male participants to other-harm. Those in the initial dual-harm group were less likely to stop harming than those in the initial single-harm groups (p < 0.05). Adverse relationship experiences generally predicted harm. A positive teacher-student bond was associated with the cessation of single-harm.

Conclusion: Single- and dual-harm in the form of physical injury typically emerge by mid-adolescence. After this point, adolescents commonly maintain harm, especially those who have presented with dual-harm. Helping adolescents cope with adverse relationship experiences and creating opportunities for positive relationship experiences could address these harmful behaviors.