NEW YORK — Whether teen marijuana users end up quitting the drug depends largely on who their friends are, a new study suggests.
The study involved 458 high school students in the United States who said they had smoked marijuana at least four times in the past month.
After a year, 19 percent of participants had stopped using marijuana.
Teens were less likely to quit if they had friends who also smoked marijuana, or if none of their friends attended their school. Teens were more likely to quit if their friends did not use marijuana, the researchers said.
A slew of other personal and family factors — such as whether participants lived in a safe or disadvantaged neighborhood or had controlling parents — held little influence over teens' likelihood of quitting, said study researcher Michael S. Pollard, a sociologist at the RAND Corporation, a nonprofit research organization.
Marijuana users tend to make friends with other people who already smoke marijuana, studies show. These friends don't induce teens to use the drug per se, but they don't help them quit, either, said Pollard, who presented his work here this week at the American Sociological Association meeting.
"They're less likely to induce you to stop," Pollard told LiveScience. [See The Old Drug Talk: 7 New Tips for Today's Parents ]
Previous studies have found adult marijuana smokers are more likely to quit if they are employed or married, suggesting that roles in adult life can conflict with marijuana use, or make it more difficult.
"The reason we don't see much predicting cessation in adolescents is…the stuff that really matters [for quitting] just hasn't come along," Pollard said.
But Pollard said that it still makes sense for public health campaigns aimed at curbing marijuana use to target adolescents. Such campaigns might teach teens about the negative consequences of having drug-using friends.
"This is a behavior that's much harder to stop when you're surrounded by people who engage in the same behavior," he said.
Although the study used surveys administered in 1995 and 1996, Pollard said the findings were very much applicable to today.
Studies show that the percentage of high school seniors who say they've used marijuana in the last year has stayed fairly constant over the last decade, and is currently at 38 percent, Pollard said. And the percentage of students who say they think the drug has great risks has fallen.
"These days, people are less concerned about the negative effects of marijuana, which suggests there may be more people in the future who are using marijuana, which then means you're going to be surrounded by even more peers using marijuana, which will make it more difficult for kids to quit," Pollard said.