How to handle ds smoking weed

[Menopausecrazy]

Ds is 16 and just finished his GCSE’s. I’ve suspected that a few times he has come home and is stoned but he has denied it. I’ve talked to him at length about how it can affect mental health and dull your brain. Also told him i’m really disappointed. Now that he has started the summer holidays he seems to be smoking it more. Not in my house but when he returns from his girlfriend. He has a part time job so he doesn’t need money from me. I’m so concerned that he is forming a habit. He already vapes which I thought was bad enough.Last night he admitted that he will smoke it once a week. Any advice on how I can get through to him please? I’m so worried but not sure how I can get through to him.

I'm not a parent but my friend has a 17 year old living with him because his Mum is a paranoid squizophrenic and his dad is just useless. My friend used to date dad. Anyway kid lives with him because it was the most stable environment he'd get, and I have a close relationship with him as a result. He's a nice kid but he started doing cannabis a year or so ago.
I had a big hand in stpping him. I approached it with NO JUDGMENT. I told him I understand the appeal, its lots of fun and relatively harmless in terms of not expensive, doesn't really do much harm to physical health (obviously smoking is bad but having a couple of joints once a week is nothing compared to 20 cigarettes a day), it is nice to bond over it with friends etc, I get it.

BUT I told him he's a smart kid, but smelling of cannabis will cause him problems at college/work, and that if he's going to do it please keep it minimum because of how it affects our developing brain. He could cause himself an uncertain future, particularly with his mum's problems and the element of MH. He did take it on board and doesn't do it any more now. He's got into his gym/fitness, which I'm really glad about.