Is it true that some pilots increase the cabin altitude slightly to calm down potentially disruptive passengers for safety reasons? For example, footballers who have just won a championship.
I've never heard of this "trick" being used or recommended, although the limits of what I've heard are pretty much limited to US commercial aviation.
If you climb the cabin from the usual 8000' to 10,000', the incremental gain in "sleepy" factor is a little bit but not all that much. If you climb it above 10,000', then you might "encourage" a few of the more tired/drunk/elderly folks to go to sleep, but now you're into the realm of operating outside of normal practices, and you need to start considering things like, the pilots both need to be on oxygen, the flight attendants may get "tired" quicker than the passengers do, anybody who is elderly or in poor health may start suffering consequences, and then there are company policies and national regulations to consider.
If you raise the cabin above about 14,000 - 15,000' depending on your specific aircraft, then you'll end up activating the automatic passenger oxygen masks, and now you've got some serious 'splainin to do! (#1, it's a bunch of work for maintenance to repack them, and the aircraft is grounded until they do, and #2 you open yourself up to all sorts of issues if you still have a long way to fly at high altitude to get to your destination!)
I'm going to guess that in the history of aviation, this sort of trick probably has been used at some point, but the opportunity for the uncomfortable questions along the lines of, "okay, tell me again, you did what exactly???" to which the best available answer is along the lines of, "um, well, it, ah, seemed like a good idea at the time, sir..." is awfully high.
I certainly wouldn't recommend it.
Not that someone may not have tried it, but it would be a patently bad idea, most likely resulting in the opposite reaction.
One of the major symptoms of hypoxia is aggression:
Behavioural changes. The person may become more verbally and physically aggressive. They may also have issues with disinhibition (ie. “socially unacceptable” behaviours). *
Add to that:
Difficulties with executive functioning , such as reasoning, judgement, initiation and impulsivity.
and your problems might get worse.
Yes, it is true that some pilots do this for that exact reason. If you're literally asking if it ever happens, you will have difficulty finding documentation, so I can only tell you what I have heard from a an aviation college professor who has claimed to have done this for the very reason the asker is describing.
When I was in college, one of the professors who would fly on behalf of the university, told us about a time that he did this to get the basketball team to calm down.
Whether or not it works, I do not know, and I have never done it nor would I because it is unethical.