I'll take the heat for throwing out that garbage rumor. That's all it is. There are some tmz and other clips where John is sauced, but who doesn't get lit every now and then.
This is my crackpot theory, ok...Farve, Kosar, lots of these dudes from this era are prone to CTE/ALS. You think QB, no big deal, right? Ken Stabler, autopsied stage 3. That dude didn't play near as much as Elway.
Then there's the fix you get from playing NFL ball. When that's gone there's a tendency to replace it.
These factors often lead to mental health issues.
I don't know that any of this is more than rank speculation. Just don't know one way or the other, but see some things and let intuition run free.
So it's an unknown but real probability that's just flapping around out there.