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A new survey from the National Institutes of Health (NIH) shows that marijuana use among young people is on the rise.

The NIH 2013 Monitoring the Future Survey measures drug use and opinions among eighth-, 10th- and 12th-graders in the U.S. This year, the major finding shows that the number of high schoolers who think marijuana is dangerous has continued to drop over the past decade. The data shows that teens are using it more often than they have in the past. And according to the researchers, such lax attitudes about pot will likely continue to lead to increased use.

This year’s survey polled 41,675 students from 389 public and private schools, and found only 39.5% of 12th-graders thought marijuana was harmful, which is down from 44.1% last year. Usage among high school seniors has increased as well. This year, 6.5% of seniors reported smoking pot daily, a slight increase from the 6% who reported the habit in 2003 and the 2.4% in 1993. While the increases were relatively small, greater usage is concerning since levels of THC, the active ingredient in cannabis, have gone up from 3.75% in 1995 to an average of 15% in current marijuana cigarettes. For a developing brain, exposure to such doses has been linked to changes in the brain and memory loss.

When the researchers asked about usage over a month, they found that 23% of seniors reported smoking in the past month, 18% of 10th-graders and 12% of eighth-graders. “We should be extremely concerned that 12 percent of 13- to 14-year-olds are using marijuana. The children whose experimentation leads to regular use are setting themselves up for declines in IQ and diminished ability for success in life,” said Dr. Nora Volkow, director of the National Institute on Drug Abuse, in a statement.

(MORE: Does Marijuana Use by Teens Really Cause a Drop in IQ?)

The survey also looked at where teens are getting marijuana, and the survey showed that increased availability of the drug, for medical purposes, may be fueling rising rates among teens. In 2012 and 2013, 34% of high school seniors who used marijuana and lived in states where marijuana is available for medical use, said they obtained the drug through someone else’s medical prescription. A little over 6% said they had their own prescription. With the first states now legalizing recreational marijuana use, officials say it’s possible that marijuana use among teens may only climb, if additional regulations aren’t put in place. “The promise was that there would be regulatory schemes to prevent marijuana from getting into the hands of children and adolescents. In every state that promise has been broken,” said R. Gil Kerlikowske, director of the Office of National Drug Control Policy, during a teleconference discussing the results.

There were some encouraging trends as well. Use of synthetic marijuana, sometimes called K2 or Spice, as well as bath salts and inhalants dropped in the past year. Cocaine and heroin use remained unchanged from 2012, but the researchers have been seeing a gradual decrease over recent years. Cigarette smoking also declined among teens. But students continued to report abusing medications for ADHD, with 7.4% of seniors taking Adderall for nonmedical reasons and 2.3% taking Ritalin.

Given the rising rates of marijuana use among teens, the survey researchers plan to investigate how new state marijuana laws that allow recreational use of the drug affect access to and attitudes about the drug for adolescents.

— With reporting by Maya Rhodan