I actually have a mental illness have had OCD all my life.So you're on 250mg of seroquel/day?
That's definitely enough to make you feel slow and "brain dead".
Maybe you have some underlying mental illness or are prone to depression (maybe it runs in your family?) but otherwise I don't think you did any damage. Specially since your friends are completely fine.
In my opinion (with the limited information I have) it's all psychosomatic and the drugs they put you on are actually making it much worse (specially the seroquel). I agree with the other BLers who have mentioned this.
Don't take this as an official diagnosis or as medical advice but definitely go talk to your doctor or maybe look for another one for a second opinion.
However something really changed that night maybe I have another mental illness I am not even sure anymore what happenned.
For now it is just an ugly fact that I am more stupid and slower.