Well .. not sure about that .... I think it is a big deal as I have seen too many people go down that road with terrible consequences, including a close friend of mine who has suffered from mental problems all her life from smoking cannabis ... nobody can say what is the right way to treat this situation, he might come through it fine and I sincerely hope so, but it is a dangerous tightrope and I think you need to talk long and hard to him, at least you can say you tried.