Changes in Sleep Patterns
These kinds of changes should be fairly obvious. Does your son stay up late (or even all night) frequently, refusing to get up in the morning at a decent time? Does your son sleep way too much or way too little? If your son isn't sleeping much, there's a good chance he is using. This is a frequent effect of this kind of stimulant.
Hanging Out With a Bad or Different Crowd Than He Used To
Your child might try and tell you that his friends are cool kids. But you need to take a close look at the kinds of kids your son is hanging out with. Chances are the way these friends behave is the way your son behaves when you're not around. Do some of your son's friends smoke cigarettes or pot? If so, odds are your child is smoking too. Your son's friends are like a mirror for your son - he looks at himself in that mirror and tries to conform to what he sees there. One of the best ways to get a good idea of what your son is like is to look at his closest friends.
Isolating from Family
Does your son act distant? Does he constantly want to be with his friends away from home? when you ask him what he has been up to, does your son give some vague reply? Does your son want to eat in his room all the time instead of with the family? Children are smart - they know that the easiest lie to tell is the one they can avoid having to tell. If your son doesn't tell you what he has been up to, there's a good chance your son is hiding something.
Excessive Use of Foul Language
Has your son suddenly developed a filthy mouth? This might indicate that your son is giving into peer pressure from his friends and should be a warning sign to you. If your son is trying to fit in with his friends by cussing, sooner or later your son will probably look for other ways to gain acceptance in his peer group. One of these ways is often drugs.
Paranoia - "Everyone is Out to Get Me"
Does your son treat everybody as if they were the enemy? Does he tend to express the idea that everybody is out to get him? Does he seem overly paranoid to you? This is not normal teenage behavior; you need to understand that. This is one of the most common signs of drug abuse. It's one of those signs you don't have to look hard to see.
Dramatic Mood Swings
Does your son seem really happy one day, then terribly depressed the next day? Do your son's emotions go up and down constantly? This is often confused with "normal" teenage behavior, but it can also be an obvious sign of drug abuse. Don't simply write it off.
Sudden Bursts of Anger
Has your son developed a violent side? Is he prone to sudden, uncontrollable fits of anger? This doesn't have to mean physically violent (though that is often the case) but can also be a teen who is always yelling or threatening people. Any of these things should be a warning sign to you that your son could be experimenting with alcohol or drugs.