Help With A Friend

i have a friend who uses drugs so often.. he smokes pot, does herion,acid,cocaine..anything you can think of. i dont know how to help him, i can yell at him because im afraid he will do something stupid jut like he has done in the past. he says it makes him happy and i've seem. and when hes not on the drugs, he depressed. he's been to rehab and over dosed..i don't know how to approach him. please, any ideas? thank you
well he needs 2 sort it out