A growing number of teens are smoking marijuana, a new study shows.
The increase is greatest among black teens. Use of alcohol and cigarettes among this age group is declining, HealthDay reports.
The decline in cigarette use was greatest among white teens, the study found.
Researchers from Penn State analyzed data from almost 600,000 high school seniors. They found past-month marijuana use rates peaked in the 1970s, declined through 1990, then rose again to reach levels of use of more than 20 percent for both black and white teens.
In 2013, about 10 percent of black teens smoked cigarettes, while almost 25 percent used marijuana. In contrast, almost 19 percent of white teens smoked cigarettes, while almost 22 percent used marijuana.
The findings are published in the Journal of Adolescent Health.
"Our analysis shows that public health campaigns are working — fewer teens are smoking cigarettes," lead researcher Stephanie Lanza said in a news release. "However, we were surprised to find the very clear message that kids are choosing marijuana over cigarettes."
While the rate of teen alcohol use has declined since the mid-1970s, white teens still drink alcohol more than they use any other substance, the researchers found. Teens were more likely to use marijuana if they also smoked cigarettes, and vice versa. Use of marijuana and excessive drinking were also linked.