Teen Marijuana Use--FYI for Parents

A new survey shows marijuana use by teens remains high, and officials say it will probably increase as a result of Washington and Colorado decriminalizing the drug last month.

“Based on what we know ... we are predicting that it’s going to go up,” says Nora Volkow, MD, director of the National Institute on Drug Abuse. “Just the fact that there are some states that have made it legal ... will send a message” to teens throughout the country.

Already, the proportion of teens who consider marijuana to be harmful is the lowest it’s been in decades, according to the 2012 “Monitoring the Future” survey of eighth, 10th, and 12th graders. The annual survey of teen drug use is conducted by researchers at the University of Michigan.

The survey's silver lining is that it shows the use of illicit drugs, alcohol, and cigarettes is declining.

Still, about 70% of eighth graders said they thought regular use of marijuana was harmful, while about 42% said they considered occasional use harmful. Those rates are the lowest since the survey began asking eighth graders that question in 1991.

Among 12th graders, the proportion who said regular use was harmful was about 44%, occasional use, about 21%. Those are the lowest rates since 1979 and 1983, respectively.

The survey shows that 6.5% of high school seniors said they smoke marijuana daily, which is about the same as last year but up from 5.1% five years ago.

Use of synthetic marijuana, known as K-2 or Spice, was stable in 2012, with slightly more than 11% of high school seniors reporting they had used it in the past year, the survey shows.

This Is Your Brain on Marijuana

Teens who think marijuana is safe to use are mistaken, Volkow says. “I think that the data are quite clear that smoking marijuana during adolescence is harmful to your brain.”

A National Institutes of Health-funded study, published in August in theProceedings of the National Academy of Sciences, found a significant drop in IQ -- an average of eight points -- between the ages of 13 and 38 in people who had been heavy marijuana users since their teens. Even those who quit using the drug showed impaired mental abilities if they had started smoking marijuana in their teens.

“Findings are suggestive of a neurotoxic effect of cannabis on the adolescent brain and highlight the importance of prevention and policy efforts targeting adolescents,” the researchers concluded.

Washington and Colorado voters approved measures legalizing possession of up to an ounce of marijuana by people 21 and older. Washington’s law went into effect Dec. 6, while Colorado’s is set to become effective Jan. 5. Medical use of marijuana is legal in 18 states and the District of Columbia.

Although marijuana is illegal under federal law, President Obama told ABC’s Barbara Walters in a Dec. 11 interview that going after recreational users in states where marijuana is legal should not be a “top priority” of federal law enforcement officials.