The Multiple Personality Repressed Memory

In the eighties and nineties, we see cases where people diagnose with multiple personality disorder recover memories of childhood abuse. Often in the form of repressed memories, which don't exist. So therefore in memories that they disassociated from and that they retained some knowledge of, but just didn't feel like it was theirs. Do people stirt use this as a defence, like an actual insanity effence? It's actually they do.