I live in Colorado, but don’t do drugs, so I have no direct experience except to say that alcohol at this altitude has a greater effect for some.
It seems to take visitors less alcohol to get tipsy than closer to sea level.
I’m not sure the altitude affects those of us who live here, though. You do get used to the thinner air eventually. I live at about 9,500 feet or so, and it bothered me at first, but hasn’t for a long time.
I get altitude sickness above around 13,000 feet and that hasn’t changed at all over the years, so getting used to the altitude does seem to have concrete limits. I’ve only hiked above 13,000 feet twice and the last time I got very ill and had to descend rapidly. I’ll never manage to hike all of the 14ers.
You ask a good question - wondering if anyone has a more definative answer?
Totally off the subject, but there are a bunch of beautiful 13ers that have the advantage of far less traffic.
A few of us had a great time climbing Mt. Rosalie. We saw only one other hiker the whole day.