The neurobiological effects of alcohol are fairly complex. I don't think most of its effects can be attributed to a single mechanism or reason. It might be tha

The neurobiological effects of alcohol are fairly complex. I don't think most of its effects can be attributed to a single mechanism or reason. It might be that coming back from the (subjectively positive) effects of alcohol could be offsetting in some cases, but I've also found that even smaller things that wouldn't necessarily trigger that much anxiety can do it sometimes after a night of drinking. I don't think it's just a disconcerting return to normal; I've sometimes noticed myself catastrophising after drinking in a way that's significantly greater than I otherwise would. I wouldn't be surprised if there were some kind of a biological reason for that, although not something singular that uniformly affects all people the same way. (Individual variance is also pretty huge when it comes to any effects of alcohol, so some people might not experience that at all.) It could of course also be that, for some people, alcohol reduces inhibitions enough to give way to your demons, at least inside of your head even if not in behaviour. That might also be a part of it.