Piracetam scare

So basically I've been seeing a few people (not a lot) complaining of being dumber after 2-4 months of piracetam and when they got off of it the effects of brain fog and being dumber persisted. They say they've tried every medical test possible that could show if there's something wrong but the results came out good. So my question is: Could these accusations be true and if so how come I've never felt this way?