Although some surveys suggest that drug use in teens has decreased since 2001, the numbers are still quite high. Over 17% of high school students admit use of illegal drugs within one month of when they were asked and more than 40% of those over 12 years old say that they have tried an illegal substance at least once.

Some signs of possible drug use include:

• Bloodshot eyes
• Persistent cough
• Pupils of eyes extremely big (dilated) or extremely small (pinpoint), nystagmus (rapid eye motion) might be a sign of PCP abuse 
• Loss of appetite (occurs with amphetamine, methamphetamine, cocaine use)
• Increased appetite (with marijuana use) 
• Sluggishness, listlessness, or constant sleeping (opiate drugs such as heroine, codeine. Or may occur when coming down off stimulant drugs)
• Hyperactivity (as seen with 'uppers' such as cocaine, methamphetamines)
• Poor school performance and increased school absenteeism
• Withdrawal from family and extracurricular activities
• Change in group of friends
• Unusual odor on breath (inhalant drugs)
• Secretive behavior
• Lying or stealing
• Slow or slurred speech (downers and depressants)
• Rapid, explosive speech (uppers)
• Unsteady gait (ataxia)

Early intervention may decrease the likelihood that drug use will continue in this population. See drug abuse and dependence and drug abuse.