About one in ten youths who start smoking become addicted within a few days of taking their first puff, according to researchers who say that even a single cigarette can lead to addiction.

Scientists from the University of Massachusetts Medical School reported that 25 percent of young smokers get addicted to nicotine within a month, and even those who smoke just a few cigarettes monthly can suffer withdrawal symptoms when they don't get their nicotine fix.

The findings were based on a study of 1,246 sixth-grade students in Massachusetts. Researchers who interviewed students about cravings, restlessness, irritability and other signs of addiction found that half of the young adolescents studied were addicted by the time they were smoking seven cigarettes a month, and some were unable to stop smoking after consuming just a few cigarettes.

"Laboratory experiments confirm that nicotine alters the structure and function of the brain within a day of the very first dose. In humans, nicotine-induced alterations in the brain can trigger addiction with the first cigarette," said lead researcher Joseph R. DiFranza, M.D. "While smoking one cigarette will keep withdrawal symptoms away for less than an hour in longtime smokers, novice smokers find that one cigarette suppresses withdrawal for weeks at a time."

"One dose of nicotine affects brain function long after the nicotine is gone from the body," he added. "The important lesson here is that youth have all the same symptoms of nicotine addiction as adults do, even though they may be smoking only a few cigarettes per month."

The study appears in the July 2007 issue of the Archives of Pediatric and Adolescent Medicine.