Actually, handedness is crucially important when considering the way the brain processes all kinds of information.  In my personal studies about posttraumatic stress disorder (PTSD) I found that the following search led me off into some fascinating areas.  If you do a Google search for ‘ptsd lateralization risk’ you will get the gist of what researchers are discovering.  In light of the risk factors for developing PTSD being greatly increased for anyone with left and/or what they call mixed handedness, I suspect that similar factors probably affect us as far as depersonalization and derealization are concerned, as well.  I don’t understand why all militaries, for example, don’t simply screen for handedness and then they would prevent serious trauma reactions if they did not send anyone into combat that wasn’t entirely right handed with a right handed parental history.  The processes that determine our lateralization or handedness are triggered as humans when we are only 4 cells old, and are the same processes that make sure all the organs of a species end up in the same place.  They tell cells to go either up or down, forward or backward, right or left as we develop.  I guess if one could put all critters in nature in a line facing the same way, they all have the same strong side and the same weak side.  (I am getting practice with this as I have been learning from being with horses how this works for them.)  Because nature used this process so effectively throughout evolution, all critters naturally know their own strong side and their prey’s weak side.  In natural order, critters don’t have time to stop and think about this as they attack or are being attacked.  I suspect that it is probably only we humans, due to our many gifts of intelligence, that have managed to survive with 10% of our species being left handed and even more being mixed handed.  How this relates to depersonalization and derealization will be discovered through further research, I have no doubt.