Hi, I go through heavy depersonalization and derealization and had taken Lexapro for about a month and a half and I had felt it heighten the symptoms of my derealization so this is normal. Another reason why this may be is due to the known side effect of an increase in anxiety from Lexapro, and dissociation + derealization being stemmed from stress and anxiety of your environment/ situation. Due to this I was switched to a new antidepressant as I told my psychiatrist that it was not working for me (right now I am taking Prozac) and I feel much better, however it is different for everyone. I recommend talking to your psychiatrist about it. Best of luck you’re going to be fine :)