I spent a lot of time during childhood in this state - but of course I didn't know it then. From my understanding, people that suffer from depersonalization usually develop this state when suffering some kind of psychological trauma. When I was a child I remember feeling "unreal" or "detatched" from my physical body. Sometimes my ears would ring and I would feel almost like I watching a movie. When I left my childhood behind it never happened again unitl I started therapy 2 years ago. When I get into talking about childhood traumas I seem to slip back into that state. The room becomes misty, my T seems far away, its very difficult to speak and I feel disconnected from myself. We do grounding techniques to become present again, but sometimes it is really hard to "come back". Its not an unpleasant feeling and I can understand now , how it is used to protect yourself from trauma. If you google it I'm sure there will be more detailed info. This is just what I understand it to be, and what I have experienced of it. I hope this has been of some help. Take care.