AFAIK DID in the medical sense is just different personality states that were locked away from one another to protect the child host from trauma. Alters aren’t necessarily completely different people but moreso like the brain accessing a different state of consciousness.
I know I'm very late, but DID is quite likely a iatrogenic disorder. That is, patients that already have various mental disorders are pressured by therapists and society's expectations of what mental illness should look like into presenting those symptoms. If you look at statistics of DID, you can see that originally a very rarely diagnosed disorder. In the 70's and 80's it was picked up both by the media and a number of influential therapists, and suddenly became much more common. Then from the 90's-00's onward it significantly dropped again. This shows how the prevalence of the disorder is very socially conditioned.
The idea that personality and maybe more crucially, memory, can be fragmented and "locked off" by traumatic events is unsubstantiated and has never been proven. Proponents of DID usually "treat" it by trying to retrieve these alleged repressed memories, usually involving sexual abuse. However, there are a bunch of issues with this approach. We now know that memory isn't a tape recorder. You don't actually remember most things that happened to you, and when you do remember is usually not a faithful reproduction of reality, but narratives that you create based on preconceptions, social forces, and things that you heard from others. Sometimes even things you see in pictures of a certain event can either reshape your legitimate memory of it, or even prompt the creation of new false memories.
Likewise, this treatment, of trying to bring up old memories, can easily lead to the falsification or creation of memories. Especially in suggestible patients, and when the therapist is pushy about it.
Here's a short review of the history and issues with this diagnoses, for anyone that's interested.
