It's typical that POIS ignorant doctors resort to diagnosis of psychosis or psychosomatic etc. Too typical!
POIS is an illness in itself and that's that! It's true, it may exist over (in parallel with) psychosis, depression or whatever else. It's also true that it's very likely to exagerate of any of these other potential problems.
In my case, there is no history in my family of any of these things, I've got a very strong "head" in that sense, yet on a couple of occasions at the peak of POIS, I felt on the verge of going out of my head!
And in a day or two, back to a good solid normal.
We have to go to the doctor's loaded with information, and if they're not prepared to look at it or take it into account, they've got a bigger problem than we do.
The only way to look at it. Turn around and walk out.