My neighbor changes alot when he drinks
My 70 year old neighbor is quite laid back and friendly on the days he doesn't drink and the days where he didn't drink the night before (he doesn't drink every day). But when he drinks, he has a complete personality transformation. He's irrationally angry, intolerant, hateful, he bites my or other people's heads off over almost nothing, and he slams and throws things.
Whenever I do laundry in the basement (his apartment is right above it), I know when he's been drinking because he just here and there stomps on the floor above me so hard it startles the hell outta me, I hear him muttering angrily to himself, and I know that both of those things he does are related to his drinking because he only belches loudly when he has been drinking. And whenever I hear the stomping and muttering, I always hear belching too. When I don't hear him stomp and mutter, and he's walking much calmer, I don't hear him belch then either.
I know that the alcohol is connected to his irrational anger. Whenever I see him in person and he's acting like a shit, I smell liquor on him. When he's acting much better, I don't. I can't stand having him as a neighbor on his drinking days, but I also know that it's hopeless asking him to stop. But he's very nice when he doesn't drink.
Is it normal for someone's personality to change so dramatically just due to whether he's drinking or not? I know that alcohol can alter behavior somewhat, but like that? Going from nice and cool to irrational rage?