In the marketplace of ideas that is the Hollywood film, teenagers and adolescents are seeing fewer product placements for tobacco and more for alcohol, new research shows.

Once a staple of the silver screen, scenes with smoking in youth-oriented movies fell by 42.3 percent in the United States between 1996 and 2009, researchers reported Tuesday in the June issue of JAMA Pediatrics. Tobacco placements also fell 85.4 percent in movies aimed at adult audiences, while the appearance of alcohol products increased in both.

The decline in product placement for tobacco products may be attributed to the Master Settlement Agreement of 1998, researchers at the Dartmouth-Hitchcock Medical Center said. The agreement forced the tobacco industry to curb its marketing while funding social marketing by anti-smoking groups. However, no such agreement has been brokered with the alcohol industry in America.

The researchers reviewed product placements and the prevalence of alcohol and tobacco products in 1,400 films that were among the most popular during those years. "In summary, this study found dramatic declines in brand appearances for tobacco after such placements were prohibited by an externally monitored and enforced regulatory structure, even though such activity had already been prohibited in the self-regulatory structure a decade before," the authors wrote. "During the same period, alcohol brand placements, subject only to self-regulation, increased significantly in movies rated acceptable for youth audiences, a trend that could have implications for teen drinking."

In the 1,400 movies, researchers found 500 tobacco product placements and 2,433 alcohol product placements. Following the agreement forced on the tobacco industry, however, tobacco product placements dropped by 7 percent per year to hold steady at 22 instances per year after 2006. During those years, overall depictions of drinking in movies remained static while appearances of alcohol brands increased from 80 to 145 per year, a jump of 5.2 percent per year.

In studying marketing and propaganda, scientists don't yet understand how such product placements affect decision-making in the brain, and data from research studies is conflicting. An analysis of research last year from six European countries found that teenagers who viewed more scenes with alcohol were more likely than others to binge drink. The researchers concluded that teenage viewers of such films also were more likely to consider binge drinking as socially acceptable - but stopped short of declaring a causal relation.

New research also shows that teenagers and adolescents are more likely to develop drinking problems the earlier they start to drink.

The study was funded by the U.S. National Institutes of Health.

Source: Bergamini E, Demidenko E, Sargent JD. JAMA Pediatrics. 2013.