Marijuana use is gaining in popularity among teens, according to Monitoring the Future, an annual survey of eighth, 10th, and 12th-graders, The New York Times reports. The survey found one of every 15 high school seniors smokes marijuana on an almost daily basis.

About 25 percent of teens who took part in the study said they used marijuana in the past year, an increase from 21 percent in 2007. Daily marijuana use is at a 30-year peak among high school seniors. The findings indicate a decline in the perceived risk of harm associated with marijuana use, according to a news release by the National Institute on Drug Abuse, which funds the survey.

R. Gil Kerlikowske, Director of the Office of National Drug Control Policy, told the newspaper he believed the increasing prevalence of medicinal marijuana was a factor in the uptick. “These last couple years, the amount of attention that’s been given to medical marijuana has been huge,” he said. “And when I’ve done focus groups with high school students in states where medical marijuana is legal, they say ‘Well, if it’s called medicine and it’s given to patients by caregivers, then that’s really the wrong message for us as high school students.’”

Cigarette and alcohol use are at their lowest point since the survey began in 1975. Alcohol use in general and binge drinking in particular continued to gradually decline among teenagers. Energy drinks continue to be popular among teens—about one-third said they drink them.

The survey found 11.4 percent of high school seniors said they used synthetic marijuana, known as “Spice” and “K2,” in the past year. This was the first year the survey included questions about synthetic drugs.

Use of prescription drugs such as Vicodin and Adderall declined, as did use of sedatives and tranquilizers, the article noted. Cocaine use also decreased.