People self harm for many reasons. Often it's to relieve emotional pain. For others it's a way to come back and prove themselves alive through a dissociative episode. For others it's a way to cause them selves to dissociate. For many people its an alternative to suicide. There are many resources on the web that discuss self harm. The Secret shame website is a particularly good resource. Here's the link. http://www.palace.net/~llama/psych/injury.html