I am interested in knowing why some people go insane in solitary confinement? Is self-talk that poisonous when it is such a useful cognition tool? He did not t

I am interested in knowing why some people go insane in solitary confinement? Is self-talk that poisonous when it is such a useful cognition tool? He did not talk much about how does a born deaf person self-talk(avoiding the word think as he say), but I am curious to know what other non-verbal forms of self-talk are out there and how fast are they?