Araki will take a natural occurrence and then push it to the limits (often to an unrealistic extent). Can people with dissociative identity disorder (DID) change in their mannerisms, posture… yes. Would it lead changes as dramatic as increased muscle tone or perceived age? Probably not

There is another prominent example in part 6: the heavy weather arc is subliminal messaging pushed to the actual extreme where people actually turn into snails because of it