Intermingled with other individuals of the species, the human mind is highly susceptible to suggestion — and particularly so during developmental phases from adolescence to teenage years to early adulthood.

In Germany, teenagers were found to be 40 percent more likely to start smoking for every 10 exposures to tobacco advertisements. Kids between ages 10 and 15 were also 30 percent more likely to start smoking on a daily basis after viewing the same number of tobacco ads.

Investigators at the Institute for Therapy and Health Research followed more than 1,300 schoolchildren ages 10-15 for 2.5 years — dispersed across 21 different schools in three regions of the country — on how often they'd seen tobacco advertising. In 2011, the pupils were again asked about the frequency of their exposures to such advertising, as well as marketing for eight other product categories including chocolate, clothing, cell phones, and cars.

Published Monday in BMJ Open, the researchers said the study further confirmed the "specificity of advertising-smoking link by comparing the effects of tobacco versus non-tobacco advertising."

One in three of the students admitted to smoking cigarettes during the preceding 30 months, but only one in 10 said they had smoked one recently. Five percent of those surveyed said they'd smoked at least 100 cigarettes during that period, while another five percent said they now smoked on a daily basis. One in three of the daily smokers were ages 14 or younger, while one in four was 16 or older.

In assessing the possible impact of tobacco marketing on these smoking rates, researchers noted that while students were less likely to see tobacco advertising than other categories, one particular brand stood out from others. Nearly half of the students had seen the ad at least once, and 13 percent had seen it more than 10 times.

Although researchers acknowledged limitations to the study, given that it was purely observational and a large proportion of the original 2,300 students had dropped out, they concluded their data supports the specific association between tobacco advertising and increased smoking behavior.

"This longitudinal study also clearly points out theimplications of partial tobacco advertising bans in countries like the [United States] and Germany," the authors write. "One-third of the adolescents in the highest tertile of advertising had rates of daily and established smoking that were double — three percentage points higher — those of adolescents in the first [third]. By contrast, assuming that the models were fully adjusted for other confounding influences, one might expect a significant further decrease in youth smoking uptake in these countries after total elimination of tobacco advertising.

Teenagers who saw the most tobacco advertising, 11-55 exposures, were approximately twice as likely to become regular or daily smokers as those who saw the fewest, less than 2-3 ads. For each additional 10 exposures to such advertising, teenagers were 38 percent more likely to become regular smokers and 30 percent more likely to become daily smokers.

Despite study limitations, the researchers said the analysis offers more support for a total ban on tobacco advertising, as advocated by the World Health Organization.

Source: Morgenstern M, Sargent JD, Isensee B, et al. BMJ Open. 2013.