dissociative DISORDERS are almost always trauma driven and result in physical changes that affect the brains "hard-wiring" as they take place during developmental stages throughout childhood.It requires a hurculean effort on the survivors part and a heroic effort on the therapists part to reroute the information and identity and affect and memory in a cognitive way that might result in a unified and better integrated personality. When we set the clocks ahead I remarked that for once the whole population might taste what its like to wonder where the time went. That second of panic because we're late for work would be multiplied x infinity to feel the experience of a victim of a dissociative disorder with amnesia.
Pardon my rather academic explanation of my own experience as I speak for myself.