iStock/ThinkstockBy DR. JENNIFER ASHTON, ABC News Senior Medical Contributor

Teens are not using drugs and alcohol as much as they used to, the latest government survey shows.

Federal health officials surveyed more than 45,000 eighth, 10th and 12th graders and found their use of everything from meth and heroin to tobacco and alcohol were all down.

Conversely, however, the National Institute on Drug Abuse says 12th grade marijuana use is up in states that have legalized its use.

So what are the signs your kids may be using?

• Look for physical and behavioral signs first, like changes in their pupils and odor to their breath or a difference in their sleeping and eating patterns.

• Are they asking for more money or missing classes in school?

While it’s always important to respect your child’s privacy, it’s more important to protect their health and their lives.

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