World-renowned addiction expert Charles O’Brien, of Penn’s Charles O’Brien Center for Addiction Treatment, says addiction is a “physical change in the brain” that causes “compulsive drug-seeking behavior.”

O’Brien’s eponymous center, part of the Penn Comprehensive Neuroscience Center, treats people suffering from addictions to substances including heroin, cocaine, alcohol and nicotine, and is also researching other things that may be addictive, such as video games or gambling.

The 2003 recipient of the Nathan B. Eddy Memorial Award for Lifetime Achievement in Research, O’Brien recently spoke with the Current about the human brain, addiction, and what can be done to treat it.

Q. Your center treats all addictive substances. Is any one substance more addictive than the other?
A. The worst addiction is nicotine addiction—cigarettes. The evidence is that the greatest proportion of people exposed to nicotine become addicted. Addiction is more than pharmacology. It has to do with whether or not the drug is legal, if your friends are pushing you to do it, and so forth. Nicotine is the most addictive because it’s a legal drug, it’s available everywhere, and people get started on it when they’re young. If you start an addiction when you’re young, it’s like learning how to play a sport or a language. You get better at it so you become a better addict in the sense that you’re more firmly addicted.

Q. What happens in the brain that causes a person to become addicted?
A. All addictions activate the reward system in the brain. This is one of the oldest parts of the brain, so that it’s almost unchanged in humans compared to reptiles and amphibians. If you stop and think about it, as you go from one-celled organisms to full-size animals, there has to be something that runs the nervous system, and so animals want to activate this reward system, and they get pleasure from drinking water, from eating food, from having sex.
Drugs activate the reward system very directly and very strongly. For example, if you put in a device to measure the release of dopamine [a neurotransmitter that affects the ability to experience pleasure] in a rat while it’s having sex, the dopamine goes up during sex. But if you give that rat cocaine, it goes up [much higher] and it activates this system very, very intensely and produces learning, because just like you learn where the water is, where the food is, and so forth, you also have the same mechanisms in activating the reward system from the drugs. And then everything associated with the drugs becomes linked to pleasure, to reward. This is the way all addictions are.

Q. Is there a distinction between physical addiction and mental addiction?
A. Everything mental is really physical. If you have a thought, if you have a feeling, that is chemicals changing in your brain. So really, it’s all physical. But sometimes people talk about psychological addiction versus physical addiction. It’s very misleading to say that. It’s all physical in the sense that it’s all occurring because of changes in your brain, and these are physical.

Q. How about addiction vs. dependence?
A. Dependence is what people get from taking sedatives or pain relievers repeatedly. Your body starts adapting to it, so that’s what we call physical dependence. And it’s not the same as addiction. Doctors get confused about this though, and this is why some doctors, when they’re treating someone with pain, they’ll withhold pain medication because they’re afraid they’re going to produce an addict, and they’ll more likely produce physical dependence but not addiction.

Q. There is an urban legend that you can become addicted to anything. Is there any truth to it?
A. You can probably become addicted to anything that excites your reward system. I like to ski and that really excites my reward system, but it’s hard to become addicted to it because you have to go all the way into the mountains. Whereas crack cocaine, you can go to the McDonald’s around the corner and find somebody to sell it to you. Theoretically, if something reliably activates your reward system, you can become addicted to it.

Q. You mentioned that we all have the capacity to become addicted. Is there something that causes one person to become addicted and not another?
A. Genes. Addiction is very strongly inherited.

Q. Rehab, it seems, is often unsuccessful in treating addiction and often results in relapse. Why?
A. Addiction is in the brain so when we put a person in rehab, you take away the drugs and they say, ‘Gee, I never want to use drugs again.’ But as soon as they leave and they are hit with the stimuli of the environment, their friends, the situation, the sights, the smells, it causes a reflex action and activation in the brain. So their addiction wasn’t cured, it was just that the drugs were taken away, but the brain changes are still there.

Q. You’ve said that no medication can cure addiction. So, how is addiction best treated?
A. We don’t treat anybody with just drugs. We use all kinds of psychotherapy. We use motivational interviewing, cognitive behavior therapy, family therapy, group therapy, 12 steps, which means Alcoholics Anonymous. We use it all but we find that adding medication improves the results.

Originally published March 27, 2008