When I was 21, one of my closest friends began taking heroin 'recreationally.' He loved the way it made him feel - it counteracted the stress of everyday life - and he firmly believed that he was smart, self-aware and disciplined enough to do it just now and then.

"It's just a media myth" that you can't take drugs and not get hooked, he told me one afternoon as we had lunch in an East Village café.

Over the next five years, I watched him, helplessly, as he deteriorated in front of my eyes. Friends planned interventions that failed; we talked to him endlessly about his problem.

Still, when he died from an overdose, it came at a time I least expected it. He had been clean for four months, had moved out of Manhattan, and was living Upstate in his parent's house.

The person I used to know was coming back to me. All of his friends, we all felt like he had dodged a bullet.

And then one night when he and a girlfriend he had met in Narcotics Anonymous came to the City for "one last party," he overdosed.

And that was it, just like that. He had injected the same amount he did when he was the height of his addiction and it was just too strong for his new clean body. He was dead at age 26 because he thought he could control his addiction.

If he had known at the start that he couldn't, would it have saved his life? Would he have stayed away and stayed clean?

I don't know, but I wish I cold live through that lunch conversation again and tell him what I know now.

I wish I could show him the hard photographic evidence - the brain scans of users - that I myself have seen.

I wish I could have showed him my film. Because the evidence is incontrovertible: being self-aware and disciplined and all that is irrelevant.

Drug addiction is a disease - like heart disease or cancer or diabetes. Yes, drug addiction starts with a behavior - the addict decides to start taking the drug.

But these other diseases have behavioral elements as well; smoking and a high fat diet can cause cancer or heart disease.

Continued on HuffingtonPost entry Filmmakers Take On Addiction - by filmmaker Liz Garbus - for more about her HBO film Addiction, see the article Facing Things That Destroy Your Life