Nora Volkow, Director of the National Institute on Drug Abuse, pinpoints genetic and environmental reasons that render some people vulnerable to drugs.

Question: Does nurture play a role in addiction?

Nora Volkow: Absolutely. Oh, absolutely. There's an enormous amount of evidence about how important nurture is in terms of either protecting or making a kid more vulnerable for taking drugs. We are in the area of genetics, so everybody tries to polarize things: it's either nature or nurture. Well, it's not either/or, it's both. And as we understand more and more how genes are marking the vulnerability of people, many instances, the way that they are marking that vulnerability, is by affecting your sensitivity and the way that you respond to the environment. So you may have a genetic vulnerability in such a way, for example, that it makes you much more sensitive to stressors. So if you have that genetic vulnerability and that you're exposed to a very stressful environment as a child, your parents are not there, they don't care about you, you are physically abused, then that combination of the sensitivity to these stressors makes you more vulnerable to taking drugs.

But on the other hand, if you have accepted that same genetic vulnerability, but you grow up in a family that is very caring, very protective, then you will not develop the vulnerability because it's that interaction of the high sensitivity to the social stressor and exposure to the social stressor that then triggers the vulnerability for taking drugs.

Now, this is, of course, very important because it shifts the paradigm from, "If I'm born with these genetics, what is it that I can do?" Well, there are many things that you can do, because it means that prevention, prevention interventions, even in those that have the genetic vulnerability, can actually have an effect in preventing the disease of substance abuse and addiction.

An area of extraordinary interest right now in research is exactly how to understand how environment, why is it that an environment that's stressful can trigger that vulnerability of a person to take drugs? What does it do to the way that the brain works? How the brain works? We're going one step even more basic, how do certain environments influence the expression of genes in the cells in the brain? I mean, just amazing the sorts of things that we can now, through science, investigate. And for example, now there's been studies shown, these are studies done in Canada by an investigator, Michael Meeney, who led this effort, showing that if in little rats, the mother is not there during the first few days, they don't have that physical touch. That silences a gene, silences a gene that is important to have activated because it will enable to regulate a response to stress. So if you don't have, during those very first few days when you are born, that physical contact, that gene is silenced, and that of course will affect all your adult life.

So here you have, it's not that you inherited the gene, it's that the environment, the nurturing question you asked me, was not there, and that directly affects the gene, that will affect your sensitivity to the environment. These are the type of questions that now through science and technologies we can start to ask and this is giving us understanding about why is it that some people, no matter what environments they are born, seem to do all right, whereas others are much more vulnerable and become addicted. And we can see one day when we will be able to tailor an intervention on the basis of someone's vulnerability. And again, I just was going to say, vulnerability not just in terms of your genetics, which you don't choose. I don't choose my genes, but you also don't choose your nurturing environment. You’re born into an environment. And unfortunately, some environments are very stressful, some kids are very, very stressful growing up, that makes them vulnerable for addiction and other behavioral disorders, where others are brought up in environments that are very, have a lot of nurturing. And that's very protective.

Recorded on November 6, 2009