Adolescents' knowledge of a peer's non-suicidal self-injury and own non-suicidal self-injury and suicidality.

These findings suggest an apparent contagion effect for non-suicidal self-injury. Awareness of a friend's self-injurious behaviours is associated with an adolescent's own self-injury and suicidality. Interventions aimed at preventing NSSI and suicidality should consider prevention of possible contagion at the school and/or community level.