Those who end up in psychosis were likely headed there anyway.
10’s of millions have smoked pot and not ended up there. Perhaps 100’s of millions.
If it wasn’t going to be pot, another substance or event would have triggered it. Extreme stress, whiskey, opioids, benzodiazepines, LSD, Ecstacy, crank.
That said, kids today should not do what we adults did as teens. The evidence is in that kids should not smoke pot.
The pot that kids (and everyone else) are smoking today is not their parent's pot. The level of THC – the main psychoactive ingredient in cannabis - is typically three times stronger today than in the old Cheech and Chong days. That is not simply mind-altering, it's brain damaging.