ObjectivesNon-suicidal self-injury (NSSI) is a common behaviour in youth with mental disorder and in the general population. While NSSI is an important predictor of suicide attempts, not all youth with NSSI experience this outcome. The objective of this study is to report on the overlap between NSSI and suicidal ideation or attempt among Canadian youth self-reporting these behaviours in the general population to define a group of youth who engage in NSSI alone. This group of youth may represent a unique clinical phenotype.MethodsWe used data from 14-17 year olds ( = 2,576) from the 2014 Ontario Child Health Study, a province-wide, cross-sectional, epidemiologic study of child health and mental disorder. Based on their responses to questions about past year experiences of suicidal thoughts and behaviours including NSSI, 6 mutually exclusive groups were created reflecting their differing profiles of suicidal thoughts and behaviours. These groups were compared to each other on socio-demographic and symptom characteristics.ResultsA total of 9.2% of youth reported NSSI, and half of these youth endorsed NSSI alone (without suicidal ideation or attempts). Both groups had significantly more females. Compared to other groups of youth endorsing suicidal thoughts and behaviours, the NSSI alone group had lower symptoms of mental disorder in all domains except for social anxiety symptoms. They also had the lowest perceived need for help of all groups.ConclusionsAbout half of youth who self-harm do so without suicidal intent, and some for as long as 1 year during adolescence. Further prospective study of youth with NSSI alone is needed, to determine symptom stability as well as incident more risky suicidal behaviour before recommendations regarding the appropriateness of minimal medical or psychological intervention for youth who engage in this behaviour can be considered. There also are important sex differences in NSSI that deserve additional prospective study.