People who dismiss the disease theory of addiction often argue that use of alcohol or other drugs is a freely chosen behavior. How can a voluntary behavior become involuntary --that is, addictive -- over time?

Researchers who study the effects of drugs on the brain now have an answer. Alan I. Leshner, PhD, former director of the National Institute on Drug Abuse (NIDA), calls it the "oops phenomenon."

In a September 2000 article published by NIDA, Leshner explains this phenomenon with a common scenario. It starts with a person who chooses to experiment with an illegal drug, for example cocaine. He wants to use this drug just once, just to see what it feels like.

However, his cocaine use does not stop with "just once." In fact, he experiments a little more. Then he finds himself using cocaine weekly or even daily. Eventually this person sees that his cocaine use has too many negative consequences. He decides to quit, he wants to quit.

Unfortunately, Leshner explains, his brain has another agenda. His brain now craves cocaine as much as his body craves water. Oops -- he is now addicted, something our casual cocaine user never anticipated.

"Every drug user starts out as an occasional user, and that initial use is a voluntary and controllable decision," Leshner writes. "But as time passes and drug use continues, a person goes from being a voluntary to a compulsive drug user. This change occurs because over time, use of addictive drugs changes the brain -- at times in big dramatic toxic ways, at others in more subtle ways, but always in destructive ways that can result in compulsive and even uncontrollable drug use.

The founders of Alcoholics Anonymous presaged this idea decades ago. They maintained that they had an "allergy" to alcohol -- an abnormal biologic response to alcohol that made it impossible for them to stop with one drink. While modern researchers may dismiss the term "allergy," they can admit that those first members of AA got one thing right: Alcoholics and other addicts undergo physical change.

A recent report from the National Institute on Alcohol Abuse and Alcoholism ("Imaging and Alcoholism: A Window on the Brain," April 2000) details one aspect of this change. Autopsies consistently show that chronic alcoholics have lighter and smaller brains than other people of the same age and gender. Drinking literally shrinks the alcoholic's brain.

But the physical effects don't stop there. Drugs such as cocaine and alcohol also affect the internal workings of the brain, the very way that brain cells communicate.

Brain cells "talk" to each other by sending and receiving chemical messengers called neurotransmitters. This constant exchange of neurotransmitters affects every aspect of our thinking, feeling and behavior. Drugs interfere with this normal exchange in many ways. For example, drugs can stop the brain from making neurotransmitters. Drugs flood the brain with excess neurotransmitters or bind to brain cells in place of neurotransmitters.

In drug addiction, these changes take place in the brain's reward system. This brain pathway creates the feelings of pleasure that result when we eat our favorite meal or have an orgasm. For the person who experiences this kind of pleasure from drugs, trying to abstain from cocaine or alcohol can feel like trying to abstain from food or sex.

Nobody raises a glass of beer or snorts a line of cocaine and says, "Here's to addiction." What they want is a good time. The "oops phenomenon" reveals that first time can turn into the next time and the next, and that "casual" drug use can turn into a disease that requires professional help.

--Published Oct. 9, 2000