Marijuana facts: breaking down the myths.

• Position: HEADS UP REAL NEWS: ABOUT DRUGS AND YOUR BODY

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Marijuana use among teens had been on the decline since the mid-1990s-until now. According to the 2010 Monitoring the Future survey, teen marijuana use is no longer declining; in some cases, it is even increasing, particularly among eighth graders, the youngest group studied.

Why? One possibility is that some teens don't see marijuana as harmful ... or at least that harmful. In fact, that same survey shows that in recent years, fewer teens think using marijuana regularly is risky at all.

Why are more teens so convinced that using marijuana isn't harmful? The answer to this question may be right in front of you--on your music player, your cell phone, your computer, or your TV. In fact, the myth that marijuana is no big deal is nearly everywhere.

"The messages getting to young people are very mixed and probably contributing to the misperception that marijuana isn't dangerous or harmful," says Dr. Susan Weiss, a scientist at the National Institute on Drug Abuse (NIDA). "We are concerned about this because we know that as teens' perception of risk goes down, their use goes up."

To make smart decisions about marijuana use and your health, you need to know essential facts about the effects of marijuana.

SCIENTIFIC FACT

Marijuana is addictive.

The main active ingredient in marijuana, THC (delta-9tetrahydrocannabinol), stimulates brain cells to release the chemical dopamine, which creates a feeling of pleasure. This effect is partly responsible for the "high" a person feels when he or she smokes marijuana. It is one of the main reasons people use marijuana again and again, which can lead to addiction.

You may be surprised to know that 1 in 11 adults who use marijuana become addicted. And the younger someone starts smoking, the higher the risk. One in six people who start in their teens will become addicted.

Marijuana use can negatively affect your performance in school and athletics.

THC affects a part of the brain called the hippocampus, which is critical for processing and storing new information, making it difficult to learn. THC also affects attention, impairing your ability to do complex tasks that require focus and concentration. These effects can last even after the high is long gone, especially for frequent users of marijuana, and that can make it harder for them to do well in school.

In fact, research has shown that compared with those who don't smoke marijuana, students who do are more likely to drop out.

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