Depersonalization is an alteration in the perception or experience of the self so that one feels detached from, and as if one is an outside observer of, one's mental processes or body. When severe enough to interefere with activities of daily life it may lead to a diagnosis of Depersonalization disorder ..owever, more specifically, derealization is the feeling that nothing is real, while depersonalization is the feeling that one is literally detached from one's body or world.