Hooked: Why bad habits are hard to break

Dr. Nora Volkow, head of the National Institute on Drug Abuse, has revolutionized how science and medicine view addiction: as a disease, not a character defect

In the battle against addiction, "just say no" is magical thinking, says Dr. Nora Volkow. She's the head of the National Institute on Drug Abuse, and after spending decades studying the brains of addicts, Dr. Volkow has determined that drug addiction is a chronic disease that physically changes the brain. Dr. Volkow has found that even images of an addictive substance, such as alcohol or drugs, can produce a dopamine response in an addict's brain, and some foods can trigger a similar reaction. Morley Safer reports on Volkow's revolutionary research into addiction, as well as on her revolutionary family history.

The following is a script of "Hooked" which aired on April 29, 2012. Morley Safer is the correspondent. David Browning and Jonathan Schienberg, producers.

What's your poison, your addiction? Is it legal or illegal? Whatever it is you're hooked on, from coffee to cocaine, smoking pot to pigging out, Nora Volkow has your number. She's the head of the National Institute on Drug Abuse. For three decades now, Volkow has been looking - literally - into the brains of addicts: not just hard drug users, but smokers and overeaters too.

Nobody knows more about how we get hooked and why bad habits are so hard to break. Dr. Volkow grew up in Mexico in a family with a famous ancestor and a tragic history. She's made history herself by challenging many of the old ideas about our addiction to addiction.

Morley Safer: What do you make of that common phrase, "Just say no?"

Nora Volkow: If it were so easy I think that we would have no problem with obesity, we would have no problem with drugs. I think we have to be honest. We've all been in a situation where we were tempted by something. And we didn't want to do it. And we didn't have the self control to stop it. For example, I love chocolates, everybody knows that. And I love also coffee. But I'm very wired person, so I shouldn't drink more coffee. But at some times, I cannot resist that. And that is because not always I have the same level of self control. So saying to someone "Just say no" is magical thinking.

Volkow's thinking has revolutionized how science and medicine now view drug addiction: as a disease, not a character defect. Her research pinpoints how drugs affect learning, memory, and above all, self control.

Nora Volkow: We know that drug addiction is a chronic disease. It changes, drugs change the brain. Physically changes it. And these changes are very long lasting, and persist for a long period of time after the person stops taking the drug.

[Technician: OK, ready to go in?

Drug addict: I'm ready.

Technician: OK, here we go.]

She's been a pioneer in using MRIs -- brain scans -- to figure out the chemistry of addiction.

[Technician: Remain still and relaxed with just your eyes closed, OK?]

This subject is a recovering heroin addict. One of hundreds of drug abusers Volkow and her staff have examined over the years. Zeroing in on a critical substance: dopamine.

Nora Volkow: Dopamine so happens to be one of the main chemicals regulating pleasure centers in the brain. And as such, it's therefore the mechanism by which nature motivates our behavior.