Q: How can I tell if my child has been using marijuana?
A: There are some signs you might be able to see. If someone is high on marijuana, he or she might:

• Seem dizzy and have trouble walking;
• Seem silly and giggly for no reason;
• Save very red, bloodshot eyes; and
• Have a hard time remembering things that just happened.

When the early effects fade, the user can become very sleepy.

Parents should be aware of changes in their child’s behavior, although this may be difficult with teens. Parents should look for withdrawal, depression, fatigue, carelessness with grooming, hostility and deteriorating relationships with family members and friends.

In addition, changes in academic performance, increased absenteeism or truancy, lost interest in sports or other favorite activities, and changes in eating or sleeping habits could be related to drug use. However, these signs may also indicate problems other than using drugs.

In addition, parents should be aware of:

• Signs of drugs and drug paraphernalia, including pipes and rolling papers;
• Odor on clothes and in the bedroom;
• Use of incense and other deodorizers;
• Use of eye drops; and
• Clothing, posters, jewelry, etc., promoting drug use.

Source: The National Institute on Drug Abuse 2010