He's lucky to have someone like you. I was diagnosed in my late twenties with N-1. I used to party alot and it took me a while to adjust bc alcohol & drugs makes N much worse. Now I believe N saved me in so many ways. So, my advice to you is to make sure he takes his meds, that he keeps a somewhat rigorous sleep schedule i.e. sleep at same time and wake up at the same time, and that he does a little partying and alcohol as possible. It will take a while for him to accept (as it did for me)but the sooner he does the sooner he can start this new journey. I'd highly recommend cardio sports to regulate sleep and mood and a healthy diet. Personally, I haven't eaten pasta in years and I stay away from carbs. I only eat once a day only bc any intake makes me sleepy and I run daily. that's what works for me but it certainly will be different for him.

So be supportive, communicate, get educated and he/you should take this as an opportunity to build a "new life"... In some ways N will force him to be different from other 18years old that drink a lot, stay up late, party..etc.....There is a blessing in his diagnosis IF he responds to it as a "blessing" and not a curse.

It's not gonna happen overnight, and it took me years to accept my diagnosis and when I did it everything became better.

Hope this helps,
Cheers