The behavioural and emotional profiles underlying adolescent self-harm, and its developmental risk factors, are relatively unknown. The authors of this paper aimed to identify sub-groups of young people who self-harm (YPSH) and longitudinal predictors leading to self-harm using the Millennium Cohort Study. (Pre-print: https://www.medrxiv.org/content/10.1101/2020.07.10.20150789v1)