A study of why teens use marijuana finds almost one-third say they use the drug to alleviate boredom, HealthDay reports.
Teens who use marijuana because they are bored are more likely to also use cocaine, the study found.
The researchers found marijuana use itself was not a risk factor for using other drugs.
While people do generally use marijuana before other drugs, it does not mean marijuana is a cause of using those other drugs, according to lead researcher Joseph Palamar of New York University Langone Medical Center.
The findings appear in the American Journal of Drug and Alcohol Abuse.
The new study focused on high school seniors who reported marijuana use in the past year. The study looked at their self-reported use of other illicit drugs, including powder cocaine, crack, heroin, LSD, other psychedelics, amphetamines, tranquilizers and other narcotics.
Teens who said they used marijuana "to experiment" had a lower risk of using any of the eight other drugs, the study found. Lead researcher Joseph Palamar said this indicates teens who say they are trying marijuana just to try it are often at low risk for moving on to other drugs.
"Most teens who use marijuana don't progress to use of other drugs, and we believe this is evidenced in part by the fact that nearly two-thirds of these marijuana-using teens did not report use of any of the other illicit drugs we examined," he said in a news release.
Marcia Lee Taylor, President and CEO of the Partnership for Drug-Free Kids, said it is important to understand what motivates teen drug use in order to prevent it.
She added some people are genetically or psychologically predisposed to addictive behavior. "I wouldn't want a parent or a teen to say, 'I'm not using for these purposes, so therefore I'm in the clear. I don't have a risk of getting addicted,'" she said.