What medicine you've taken in past? I had antiepileptics cuz I as a baby had sleeptime cramp seizures confirmed by eeg, they stopped it, after taking for years (1st had to try different ones till found 1 working) eeg showed 0 abnormal reaction in response to flickering light so took light ssri 1 year as it was said to do so to transition to medicine free state at 15, I'm ok now. Had antibiotic at 6 to stop near-pneumonia from going full, had 40c temp. Don't recall any other medicine. For some maybe something they took in past altered body making POIS be.