A new U.S. study suggests 10 per cent of young people who become dependent on nicotine do so within two days of smoking their first cigarette.

The four-year-study, published this week in the Archives of Pediatric and Adolescent Medicine, also found 25 per cent of young people became hooked within a month.

Researchers monitored 1,246 Grade 6 students in six Massachusetts communities over the course of four years.

Scientists found the teens began to feel withdrawal symptoms even if they smoked only a few cigarettes a month. Among the 217 students who had smoked, more than half became addicted by the time they were smoking seven cigarettes a month.

The students experienced symptoms of withdrawal such as restlessness and irritability, which is contrary to the long-held belief that only people who smoke five cigarettes per day or more, experience withdrawal symptoms.

"One dose of nicotine affects brain function long after the nicotine is gone from the body,'' Dr. Joseph DiFranza, leader of the research team at the University of Massachusetts Medical School, said in a release.

"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.''

Researchers said during the beginning stages of addiction, one cigarette can relieve withdrawal symptoms for up to a month. Once tolerance to the drug builds, more nicotine is needed to cope.

"While smoking one cigarette will keep withdrawal symptoms away for less than an hour in long-time smokers, novice smokers find that one cigarette suppresses withdrawal for weeks at a time," explained DiFranza.

Addiction-related changes in the brain caused by nicotine are permanent and remain years after a smoker has quit.

One cigarette can trigger an immediate relapse in an ex-smoker. Even smokers who have abstained for many years will need to smoke several cigarettes a day to keep the cravings under control.

The National Institute of Health estimates 6.4 million children living today will die prematurely as adults because they began to smoke cigarettes during adolescence.

The World Health Organization suggests tobacco kills more people than AIDS, legal drugs, illegal drugs, road accidents, murder, and suicide combined.

The most recent numbers from Statistics Canada suggests teens are smoking less than ever before.

• Among youth 12 to 17 years of age, the proportion of smokers in this age group fell from 14 per cent to eight per cent from 2001 to 2005.
• In 2001, 73 per cent of young people said they never smoked cigarettes. In 2005, the percentage rose to 82 per cent.