From Teen Mental Health.org:
"Non-Suicidal Self-Injury (NSSI), commonly referred to as self-injury or self-harm, may be confusing and difficult to understand. Many people have a hard time talking about self- injury because it seems unnatural to them. It is important to understand what motivates someone to harm themselves because not all people do it for the same reason. The best way to help someone to stop self- injuring is to help them address the underlying issues."
Click for links:
Adolescent Self Harm (from the American Association for Marriage and Family Therapy)