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Researchers: 3 of 4 smokers get addicted

Will tougher cigarette warnings work?

The Liggett Group's agreement to mark its packages with a warning that cigarettes are addictive comes after 30 years of increasingly somber cautions about the danger of tobacco.

During that time, cigarette smoking has dropped by half among adult males and by one-third among adult women. But it is increasing sharply among those in their teens, when the habit is usually picked up.

In fact, teenage smoking increased by 30 percent from 1991 to 1995, according to a study published Thursday by the Stanford University School of Medicine.

"Sizable proportions of adolescents are not seeing, reading and remembering cigarette warning labels," the Stanford report said after surveying 1,700 high school freshmen in San Jose, Calif. "Knowledge of warning labels was not associated with subsequent decreased smoking."

The labels currently say smoking causes cancer, emphysema and other diseases, but they do not mention addiction.

Researchers say that three out of four people who start smoking become confirmed addicts, and 90 percent of those who try to quit each year fail.

A major part of the reason is that nicotine is as addictive as cocaine and heroin, and even more habit-forming than alcohol, say scientists who study addiction.

Using modern electronic brain-scanners, researchers can see how chemicals in tobacco smoke permanently change the way brain cells, called neurons, communicate with each other. The changes alter the function of neural circuits that regulate mood and behavior.

"Prolonged drug use changes the brain in fundamental and long-lasting ways," said Alan Leshner, director of the National Institute on Drug Abuse. "Addiction is a brain disease."

The changes make it extremely difficult _ and often impossible _ for people to quit.

Last year, President Clinton authorized the Food and Drug Administration to regulate nicotine as a dangerous substance.

Nicotine itself does not cause disease. It is the other toxic substances in tobacco smoke _ chiefly tar and carbon monoxide _ that lead to cancer of the lungs, throat and other organs.

But nicotine is indirectly responsible because it makes it so hard for smokers to quit.