Sudden bursts of anger. This doesn't have to mean physical violence but can also be a teen who is always yelling or threatening people. Any of these behavior patterns should be a warning sign to you that your child could be experimenting with drugs. If you suspect that your child is not telling you the truth on an on-going basis, there is a good chance that your instincts are accurate. Be persistent and learn what it is that they are trying to cover up.
Drugs are always a possibility.
Dramatic mode swings. This is often identified as normal teenage behavior - and it may be, but it can also be a sign of drug abuse. Excessive money requirements or money disappearing. Drugs cost money - lots of money. If your child keeps coming to you needing money, or if money keeps disappearing from your purse or wallet, you need to have a serious talk with your child.