why do you think this is self injury? i'm not saying it isn't, but it could be just, well, sort of a "hobby" i guess. it really depends on his reasons for doing it.

there are many motivations for self injury--it's a highly individual thing. consequently it's really impossible to just give a brief explanation here. however, the secret shame website (http://www.palace.net/~llama/psych/injury.html) is a good place to start for general self injury info. you could also check out the friends and family forum on bodies under seige (http://busmail.org/phpBB/index.php). this is an area where friends and family members of self-injurers can ask questions and get support. you have to join to post, but anyone can read.