Have I done permanent cognitive to myself?

I’ve been on 400 mg hydroxyzine for three months, and then accidentally took 600 mg for a while. I thought it was relatively safe but now I’m finding out it can cause you to “get dumber”. I’m 22F if that matters. Did I fuck up?

(They’re switching me to promethazine now that I’ve developed a resistance to hydroxyzine. I hope that doesn’t have the same issue lol)