I had psychosis before any medication or doing any drugs, but while I was in the hospital they raised one of my medications to the maximum dose (Risperidone), and I had an unusual reaction of delirium. I kept thinking I was in different places: thought I was lost in the woods in Maine, on a boat, in a hospital with wayyyy more hallways than the one I was in (and was lost), thought I accidentally broke into an apartment in Lowell, MA and was going to get shot. I thought it was raining cocaine. I thought they kept switching the rooms around to confuse me. At one point, I felt so lost that I just stood in one place in the hallway for like an hour crying and anytime anyone asked me what was wrong I would just say "I'm lost."
I was told this was such an unusual reaction they had to report it to the FDA.