The brain's first response to nicotine can be a telltale sign of whether a young smoker is at risk of addiction, according to researchers at the University of Massachusetts Medical School.

Reuters reported Oct. 1 that researcher Joseph DiFranza and colleagues said that adolescents who get a feeling of relaxation after taking their first few drags on a cigarette are likely more susceptible to the effects of nicotine and more at risk of becoming addicted to the drug.

"We know that nicotine can have an immediate impact on the brain, and yet we also know that not every adolescent who tries a cigarette gets hooked," said DiFranza.

Researchers studied a number of predictors of nicotine addiction among 1,000 teens attending schools in Massachusetts, and found that an initial sensation of relaxation was the strongest. Others risk factors for addiction included a depressed mood, novelty-seeking personality, and familiarity with "Joe Camel," the former animated pitchman for R.J. Reynolds' Camel cigarettes.

"The Joe Camel campaign was discontinued in August of 1997 as our subjects entered 2nd grade (around age 7), suggesting that the deleterious effects of cigarette advertising persist long after the exposure," the study said.

The research was published in the October 2007 issue of the journal Pediatrics.