Also, as a personal preference, I am trying to get away from talking about any of this as "mental". We don't even have proof the mind exists. We know the brain exists. So I prefer to talk of cognitive deficits, or brain deficits, rather than mental deficits. When you are trying to reason about these things and use the word "mind" you add a layer of ambiguity and distortion.
If I were going to use the word "mental" at all it would, ironically if you know my background, be about false belief systems. I use that not in the sense of false beliefs causing disease, but about how much of what we think and reason about the world is probably and sometimes provably wrong, and sometimes just problematic. The extreme case here would be someone who is indoctrinated by a cult. Their brain is most likely fine, but what they believe is highly distorted. Similar but weaker arguments sometimes apply to choice of religion (including atheism), political party, music or sports team. Why is your football team the best team in the world? Why is your preferred political party so good?