"Sleeper effect" of cigarettes can last for years

Trying just one cigarette may not be so harmless for non-smokers after all.

Scientists have discovered that a single cigarette has a "sleeper effect" that can increase a person's vulnerability for three years or more to becoming a regular smoker.

"We know that progression from experimenting with one cigarette to being a smoker can take several years," said Jennifer Fidler of University College London.

"But for the first time we've shown that there may be a period of dormancy between trying cigarettes and becoming a regular smoker -- a 'sleeper effect' or vulnerability to nicotine addition," she added.