A friend's daughter began doing this in her early teens. This followed the death of her twin sister from leukemia a couple of years before after a five year battle during which the family was dominated by the need for Sarah's treatments. Her sister, when Sarah was dying, told her brother that she wished she would hurry up and die. When it happened the poor kid was totally lost in guilt and that, eventually, led to the self mutilation.

Her mother got her help relatively early on and she's a lot better now, although she still has her 'blue' periods from time to time.

There seem to be many causes of this problem but it does seem to come down, in the end to a lack of self worth. I think that there is a lot more pressure on kids now to conform to ideals of one kind or another, from parents, teachers, their peers and the media, which pushes pictures of what one should look like, the way to behave, what one needs to be 'in'.