I'd argue that any teenagers who go from having access today to not having it tomorrow are probably not going to magically become different in the ways you desire; it seems a lot more likely to have effects on kids who are younger and haven't already been influenced by it, but at that point we're actually talking about trying to make a structural changes to make things different in the long term. That type of thing seems very strange to enact by making a blanket regulation on the supposed victims of the harms than on the perpetrators of it.