I agree with luke, except my classification is even simpler: I think there are just two types of cannabis smokers: those who do it for 'time out' from lives they basically enjoy, and those who do it to 'opt out' of lives they basically hate.
Someone in the first group is likely to manage their drug use so it doesn't interfere with the rest of their life, smoke at weekends or occasionally, rarely do it in public, take drugs for pleasure or to celebrate, and if they 'overdo' it, they'll learn from that and be even more careful in future.
Someone in the second group doesn't manage their drug use well, smokes in the morning before school/work, is stoned/otherwise off their head in public, binges frequently, isn't always fussy about what they take, gets wrecked for pleasure but also (perhaps more often) to deal with difficult emotions like anger, boredom and fear.
If your teen is in the first group, he'll probably be OK. If he's in the second, he's likely to have problems at school, with the police, and risks to his physical and mental health are much higher too.
The trouble with teenagers is, because they aren't always good at judging risk and like to do what other teens do, they can slip from the first group to the second.
As a parent, I think you can help by...
- Making sure they have things in their life they enjoy and that they need not to be stoned for - whether that's sport, music or whatever. You need to remember that it has to be something they enjoy and want to do, rather than something you want them to do and think is important!
- Helping them be as well informed as possible - which means you have to deal with your own fears and 'freak outs' privately, so they feel they can talk to you openly.
My own son slipped from the first group to the second, and we had some really nightmarish times... But he found something he wanted to do, and recognised the 'bad side' of drugs as well as the fun side, and has now got himself back on track... Which will maybe give hope to parents whose kids are struggling still...