Friend needs help

so i have this really close guy friend and we were talking about our deepest secrets, i told him how i used to cut and he told me his thing is worse. but he wouldnt telll me what. he aid its not on the guidlines of cutting, and he said its not something he did or something someone did to him. not drugs, not sexuality, not abuse. he said its something he hides well and hasnt told anyone and that its something he could get counseling for. Im very worried about him and not sure what to do. Any ideas?