If an eleven-year-old child smokes just one cigarette, the urge to smoke lingers within that child for the next three years, doubling the chances that he/she will become a regular smoker, say researchers from University College London, Department of Epidemiology and Public Health.

Researchers are calling this 'dormant vulnerability' the 'sleeper effect'.

You can read about this research in the journal Tobacco Control.

This is the first study to show the link between past and future smoking behaviours, said Jennifer Fidler, team leader.

The team gathered data on 5,863 children from South London, they were aged 11-16 and had taken part in yearly surveys. Saliva samples were taken and tested for cotinine - a chemical which indicates the person has been consuming nicotine. Comprehensive data regarding smoking habits of 35% of the children was gathered.

They found that 14 year-old children who had tried just one cigarette when they were 11 were twice as likely to be regular smokers, when compared to children who had not tried a cigarette at 11. These 14 year-old kids had not taken up smoking for three years, said Fidler.

In other words, they are talking about children who had had one cigarette at 11, none for three years, and then became regular smokers when they were 14.

The researchers said that whether the parents smoked or not had no significant bearing on the likelihood of a 14 year-old being a regular smoker - what influenced the chances was whether they had smoked that single cigarette when they were 11. Factors such as sex, ethnicity and socioeconomic status did not influence the results.

Fidler suggested that more focus should be centered on encouraging children to avoid that first cigarette. Something health experts, parents and educators have to bear in mind. If you can stop children from ever smoking that single cigarette they are much more likely to become lifetime non-smokers.

Fidler added that health care providers and people designing interventions must include teenagers who look as though they are going to be lifetime non-smokers, but had that cigarette some years ago.

The majority of regular adult smokers say that they started when they were teenagers.

On reading this article, adult ex-smokers must be wondering how long their urge will linger for - if it's three years for a single cigarette, what is it for someone who smoked 20 a day for 20 years?