Two pathways to self-harm in adolescence

The behavioural and emotional profiles underlying adolescent self-harm, and its developmental risk factors, are relatively unknown. We aimed to identify sub-groups of young people who self-harm (YPSH) and longitudinal predictors leading to self-harm. Participants were from the Millennium Cohort Study (n=10,827). A clustering algorithm identified sub-groups who self-harmed with different behavioural and emotional profiles at age 14. Feature selection analyses were then used to identify longitudinal predictors of self-harming behaviour. There were two distinct sub-groups at age 14: a smaller group (n = 379) who reported a long history of psychopathology, and a second, much larger group (n = 905) without. Notably, both groups could be predicted almost a decade before the reported self-harm. They were similarly characterised by sleep problems and low self-esteem, but there was developmental differentiation. From an early age, the first group had poorer emotion regulation, were bullied, and their caregivers faced emotional challenges. The second group showed less consistency in early childhood, but later reported more willingness to take risks and less security with peers/family. Our results uncover two distinct pathways to self-harm: a psychopathology pathway, associated with early and persistent emotional difficulties and bullying; and an adolescent risky behaviour pathway, where risk-taking and external challenges emerge later into adolescence and predict self-harm. These two pathways have long developmental histories, providing an extended window for interventions as well as potential improvements in the identification of children at risk, biopsychosocial causes, and treatment or prevention of self-harm.