I expect there will be higher cases of psychosis happening on intense retreats, but as anecdotal as this, I had it happen to me (albeit not as extreme as OP) after meditating for much shorter periods (approx 10 minutes up to an hour).
I really did not see it coming. For some context, I don't know of any deep seated trauma that I have and I liked to think of myself as someone robust mentally.
I experienced a deep realisation that our thoughts manifest from nowhere and not from ourselves (words fail me here) and that the construct of 'me' was completely false and was just a reverberation of my environment. I understood there was no me. This was really nice for about two weeks. I started to think that I should be looking to help other people and become a guru, perhaps write a book to help humanity, but then my ego (I expect) came back with a vengeance, kicked my ass and brought me back down to earth with a crash (maybe its a safety system). I experienced huge panic attacks like I have never had before, I carried this constant feeling of absolute dread in my soul, like a sense of impending doom. I have heard it described as the dark night of the soul. Some try to push through this, but I held back as i cannot afford to have a complete meltdown as I need to care for a young family and hold down a job.
I spoke with a well respected meditator about this, and they said the some people are wired to have an accelerated experience and are able to obtain deep introspection with limited time on the cushion.
I would say I am almost back to normal now. I had to stop all meditation and instead focused on health food, sleep habits and lots of exercise. My main mediation type thing is now running, it quietens my mind, but the grounding effect of the movement keeps me in a safe play pen to explore my reality.
meditation is incredibly powerful, in the west we have confused it as being a corporate stress ball that you squeeze or like a lavender scented, candle lit bath while listening to Enya. The truth is, it can reveal incredibly deep seated aspects of ourselves that we are in no way prepared to witness, let alone accept.