Is it usual for people's behavior to get a little bit weird if they spend too much time alone?

I don’t mean is it “normal” because I don’t know what that means. Rather, is it common?

It seems to me that when someone self-isolates too much for too long, social awareness seems to drop off pretty fast, and they start to act in ways that increase their isolation: odd mannerisms such as grimaces and gestures, less intelligible speech, poorer table manners, etc.

Is this a recognized phenomenon, or is my observation too limited?

Tags as I wrote them: social behavior, isolation, eccentricities, mannerisms, social awareness, veneer of civilization.