Not a sign, I think, though maybe a symptom.
Consider drugs that have among their effects “delusions of sobriety” (there are such). A person who takes them is apt to think his behavior seems normal, even though to others it does not. He may claim he hasn’t taken anything—may even think it’s true because his short-term memory has lapsed. But anyone can see he’s loaded. His behavior is erratic and possibly bizarre, and he doesn’t realize how far out of phase he is with consensual reality. His distorted self-perception is a symptom.
In contrast, I think I’m sober, and I am. I haven’t drunk or used anything to make me otherwise. The fact that I can claim to be sober doesn’t mean that I’m actually on something. It’s not a sign of intoxication.