To the contrary. There are many clinicians who firmly believe in the ability of the brain/mind to separate out different aspects from the other aspects of a person. It isn't "no idea" regarding that it does occur, to these. HOW the brain does it is not even no idea, but we sure don't know exactly how.

There are many doctors who prefer to write it off as a phenomena of the mind, and desire of the patient to not "own" the memories so they produce these "others." And, there are some who downright say it doesn't happen and the patient is pretending.

Now, here really isn't the place for a long discussion, other than to encourage you that no matter what the label, you are still you.