Lead author Dr. Jennifer O'Loughlin analyzed data from 319 Montreal teens who completed reports on their smoking habits every three months for five years.

The study, published online in the American Journal of Public Health, found that teen smokers progress through stages or milestones in their attempts to stop smoking.

The stages are:

-- Confidently declaring that they have stopped smoking forever, one to two months after their first puff.

-- Expressing a conscious desire to quit.

-- Over the next two years, as cravings and withdrawal symptoms increase, gradually losing confidence in their ability to quit.

-- A year later, they are smoking daily and realize they still smoke because it is very hard to quit.

-- About two years after starting to smoke cigarettes daily, teen smokers are showing full-blown tobacco dependence.

The study found that more than 70 percent of the teens expressed a desire to quit, but only 19 percent actually managed to stop smoking for 12 months or more by the end of the five-year study.