Bumbaclot, how can you say weed is not addictive?
My brother started smoking weed when he was 14, he hid this from his family until he was 16, by which time he was well and truely hooked.
Fast forward 11 years to now.
He has no job, living (barely) on benefits, no self-esteem, has a split personality, shakes badly, is aggressive and occasionally violent, he will choose buying weed over buying food.
He doesn't drink and rarely has.
I don't actually know who my brother is any more, all I can see in his personality is weed and how he will get his next drag.
He is in the minority, most of my friends and family dabbled here and there and most of them got on with a 'normal' life and out grew the usual teenage experimental phase.
But, my brothers life revolves around weed and only weed and he frequently talks about ending his life. One of my friends has been sectioned regularly through his adult life which is drug induced. And one of my friends gassed himself in a car after a physcotic episode.
OP, in answer to your question smoking weed is very normal and most people get through those early years being undamaged by their experimental stages and if they continue to smoke or do the odd line now and then, they do it while having a 'normal' happy life.
But don't for one minute not be worried or be concerned, for the minority like my brother and my two friends weed/drugs has been totally devastating.
Make sure you and your son knows the facts, and encourage him to choose a healthy happy life over drug use. Ultimately you won't be able to stop him trying weed but just make sure you are very aware of the consequences for some.