Sara Bellum
April 23 2010

In a recent Drug Facts Chat Day, Jiacalone_01 from Cashmere High School in Washington asked: What percentage of 9th graders smoke marijuana?

Not So Popular

Most teens are not smoking marijuana. We know this from asking teens themselves. How? Through the annual survey of teen drug use called Monitoring the Future, which surveys 8th, 10th, and 12th graders about their drug use and attitudes. The survey found that about 12 percent of 8th graders reported marijuana use in 2009 compared to about 27 percent of 10th graders and 22 percent of 12th graders. 

The survey also showed that marijuana use has declined steadily since the mid-1990s until about 2002. Since then, it’s kind of leveled off, so the people here at NIDA are trying to figure out why, and how to get things back to a downward trend.

The ABC's of THC

One reason for the leveling off may be something else the survey found—which is a change in attitudes among teens toward marijuana smoking—that they consider it to be less harmful than they did in years past.

The thing is, marijuana is more than just a mix of dried leaves from the cannabis sativa plant. It actually contains a chemical called delta-9-tetrahydrocannabinol, or THC, along with about 400 other chemicals. Although many of these can affect your health, THC is the main psychoactive (i.e., mind-altering) ingredient. (In fact, marijuana’s strength or potency is related to the amount of THC it contains, which is something people who use marijuana won’t know since it's an illegal substance.)

THC alters the way your brain functions, which can be bad news for teen brains since they’re still developing. For example, THC can disrupt what goes on in your hippocampus, which can lead to problems with learning and memory—since that’s what this brain area gets involved in. Disrupting its normal functioning can lead to problems studying, learning new things, and recalling recent events.

Get the Facts

You can read more on marijuana here:

P.S. Some people argue that marijuana is not addictive. Wrong! In 2007, the majority of youth (age 17 or younger) entering drug abuse treatment reported marijuana as their primary drug abused. We admit that, we still don’t know everything that marijuana use does to teens. But we do know that adolescents’ brains are still growing and changing—so is it really worth the risk?

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