TUESDAY, May 28 (HealthDay News) -- More movies approved for young viewers are showing alcohol brands, a trend that could influence teen drinking, researchers say.

Children's exposure to movie imagery of tobacco and alcohol has been linked to smoking and drinking at a younger age, heavier drinking and alcohol abuse, said the researchers from Dartmouth University Geisel School of Medicine.

Still, some good news emerged from their study: Fewer movies intended for young audiences show tobacco brands.

The researchers determined tobacco-brand exposure dropped significantly after they examined 1,400 films produced after the Tobacco Master Settlement Agreement took effect in 1998. That agreement, between major tobacco manufacturers and most of the United States, changed the way tobacco products were marketed and provided for funding of anti-smoking campaigns by tobacco companies.

For the study, published online May 27 in JAMA Pediatrics, the research team analyzed the top 100 box-office movie hits released in the United States from 1996 to 2009.

Tobacco brand product appearances declined by 7 percent each year until 2006, the study found. From then on these placements remained stable at 22 per year. The Master Settlement Agreement also led to a 42 percent decrease in tobacco screen time for youth-rated movies and an 85 percent drop for films intended for an adult audience.

Alcohol placements, on the other hand, are self-regulated by the industry. The study showed these product placements have increased from 80 to 145 each year in movies rated acceptable for young viewers. This represented an increase of 5.2 appearances annually from 1996 to 2009, the researchers noted.

"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 study's authors wrote in a journal news release.

"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," they said.

More information

The American Academy of Pediatrics provides more information on the link between alcohol in movies and teenage drinking.