Is it a common metaphor?

The description is not a metaphor. “Lost my marbles” is a common one for psychosis, dementia and the like, though.

I know I'm being overly sensitive but I'm baffled at the downvotes on my post asking for clarification :/

You asked if it was a common metaphor in reply to someone saying it is not a metaphor. Perhaps you replied to the wrong comment by mistake?

If it's any consolation, I interpreted your question as "outside of this person's experience". It seems fair to ask the seemingly knowledgeable eurasiantiger such a question. In the interests of charitable interpretations.

It is not a metaphor.

Psychotic episodes are typically marked by delusions and hallucinations caused by things like sleep deprivation and stress leading to excess catecholaminergic activity, which causes the brain to temporarily misinterpret the senses and construct delusional logic around the interpretations in an attempt to form a cohesive internal narrative of the experience.