First, how are you sure it's correlation and not causation? Perhaps he's being driven to porn/developing the habit as self-medication?
Also, as to your previous point that it will lead to "harder" stuff, a recent study says no. Yes, there will be more opportunity and exploration of the topic, but that's something that will happen eventually to all individuals. It isn't studied very well, but at least this initial one says we don't naturally become more tolerant and require "harder" pornography over time.
https://www.lehmiller.com/blog/2018/2/5/can-you-build-up-a-t...
There is more to it, and it's hard to pinpoint cause and effect. He did have issues that existed before the pornography habit. But they worsened significantly since the month he started looking at pornography regularly. I do believe that his pornography habit has lowered his mental and emotional intelligence by a noticeable factor. I also look back at when I was his same age, and see my own struggles as very similar to his. So I could be mistaken with some of the internal presumptions I've made about him, but the external ones match up almost exactly.
OK, fair enough. Hope you guys figure out an appropriate intervention plan then. Is going to a therapist on the table? Sounds like there's something deeper going on and just cutting off the porn doesn't usually solve it in my experience.
Also, as to your previous point that it will lead to "harder" stuff, a recent study says no. Yes, there will be more opportunity and exploration of the topic, but that's something that will happen eventually to all individuals. It isn't studied very well, but at least this initial one says we don't naturally become more tolerant and require "harder" pornography over time. https://www.lehmiller.com/blog/2018/2/5/can-you-build-up-a-t...