I suspect I had one (psychosis, to be exact).

I was ~13 or 14 when it started. I started getting these weird pressure headaches; they didn't hurt, so I hesitate to call them headaches, but it truly was like there was a ton of pressure in my skull. And, for some reason, I started to think that the pressure headache was associated with a certain spot on our property. Partially, I think this was because I got the uncanny feeling I was being watched there. And, at least for a little while, I was able to logic myself out of that thought...

Until, of course, I gradually wasn't. I had felt like I was being watched for months and, after a bit, I wasn't able to explain it away. Especially not when, sometimes, I felt like the thoughts in my head were not my own. Sometimes, it felt like I thought something and then the next thing I heard in my head was not my own thought. I became convinced there was something watching me and the thought made me extremally paranoid.

The fucked up thing was, my parents eventually found out and did nothing to help me. The most they did, since they had found out about my long standing suicidal ideation at the same time (since I had written about both it and my paranoia in a journal they then read), was put away anything I could use to kill myself and talk to me about my paranoid feeling. But there was no therapy, medical professionals, etc, involved. And in fact, honestly, I feel their actions worsened things for a bit because I felt like I was being watched by them all the time as well (as they were afraid I would still find a way to kill myself, despite that I had said I didn't actually want to go through with it).

Eventually, I think a few weeks after the talk, I was able to start applying logic to the situation again. The pressure headaches gradually lessened and eventually it was gone. And, with it, my feelings of paranoia.

I have no idea what is up with that. I don't know if it actually was psychosis; I just know I once read about psychosis, after I had moved out, and I had experienced many of the same symptoms described.