For a period of my life someone poisoned me with drugs that affected my brain and thought processes. I don’t know what the drug was but I definitely know it happened.
That experience is the basis for the following speculation: a lot of mental illness is fundamentally characterized by tunnel vision or what I might rather call “bright room” vision.
At the time I could not see it but looking back after the poisoning stopped I can see that my brain compensated for the poison’s toxic effects by ignoring large areas of information. This was not a conscious decision. It was just what my brain did to survive.
In this sense, my brain was in a tunnel or a bright room outside of which I could see virtually nothing. I think of the tunnel as fairly bright. That part of my world was clear enough to me. What was missing was the much larger world outside of the tunnel.
If you have ever been in an underground train station with lit tunnels going to various trains (like Grand Central Station in NYC), that is a good example of this metaphor.
Now, think about people you have known who are suffering mental illness, especially those who are not aware of their plight. Do you notice that for many of them what they see is like that tunnel? It’s bright and the way is sort of clear, but the larger environment around them is highly reduced. For me, it was more like a bright room with a fair amount of stuff in it and people and things going on, but all I could see was the inside of that room and almost nothing beyond. Outside the windows everything was dark.
I was not fantasizing the room or actively deluded by it as much as confined to it, unable to be aware of what was outside it. My brain was ignoring large sections of reality to hang on to whatever I could.
Consider a long-term alcoholic, a victim of self-poisoning, whose eyes still glow. I think what people like that see is a bright room or tunnel and not much else. How else can someone who has been addicted to alcohol for fifty years still deny it? It’s because that larger awareness is not inside their bright room.
Consider a narcissist in roughly the same way. I would maintain that they really cannot see what they are doing in the wider context of all the people they are harming because they only see the bright room around them, the bright tunnel before them.
Borderline, neuroticism, and bipolar, especially in the manic stage, are much the same.
I am not saying that all mental problems have this bright room/dark world aspect but I believe many of them do.
Incidentally, all psychologists and medical professionals should always consider poison as a significantly probable etiology for all mental illness.