Drug Abuse And Treatment

I watch intervention and thought I should write or call them on my cousin. But, I'm not sure if it will work because it seems that people on this show are extreme addicts. My cousin is 21, in college, have a job, but the abuse of drugs and alcohol. I have spoken to his family and him, and he has done almost everything. He has regularly used drugs and alcohol since he was 15 years. He does not steal to get drugs or something, and he believes he has a good head on his shoulders. But I think he did too many drugs for too long. He seems to point the finger too (he has a hard life) and blame their mistakes on others. The worst thing is, it seems mainly to blame, so I do not know how an intervention would help if the people he accused told him to quit drugs. Any ideas?