MPD: Why Not?

My theory of Multiple Personality Disorder is entirely logical, yet the producers have stated that the show isn't happening in a person's mind. Yet, if you think about it, MPD explains the character's connection, the impossibilities, the flaws, the hallucinations, and the repetitive names and numbers. If I was to stick with ONE unifying but unusual theory, it would be MPD; especially with movies like "Identity" that are very similiar to Lost.