Those are some of the results published in the annual Monitoring the Future study, a survey of more than 45,000 8th, 10th, and 12th graders from 395 public and private schools. It was released Wednesday.
Each year, the survey gathers information from teens about their use of alcohol, drugs, and tobacco, as well as asking them questions regarding their attitudes about the drugs.
This year, 6.5% of 12th-graders said they smoke marijuana daily. That's slightly down from 2011, when 6.6% said they smoked it daily.
Teens' perception about the harmfulness of using marijuana was down, which may signal future increases in marijuana use, according to the study's principal investigator, Lloyd Johnston.
Overall, 41.7% of eighth-graders perceive occasional marijuana use as harmful and 66.9% see regular use as harmful. As teens get older, their perception of harm decreases, the survey showed, with only 20.6% of 12th-graders seeing regular use as harmful.
"Marijuana use that begins in adolescence increases the risk they will become addicted to the drug," says Dr. Nora Volkow, director of the National Institute on Drug Abuse, in a statement. "The risk of addiction goes from about 1 in 11 overall to about 1 in 6 for those who start using in their teens, and even higher among daily smokers."
Image: Smoke, via Shutterstock