I believe that depending on the severity and nature of the psychosis, and how it is handled by others, it can be traumatic. And trauma does change the brain. I don't think it is really brain "damage" but I also think subjectively one could feel like it is damage if the effects are negative. If you look up studies on how trauma changes the brain, I think it is kind of like that. Because I know I have had a couple psychotic episodes that were traumatic.