Does Dissociative Identity Disorder exist?

I just finished watching Monsters Inside: the 24 Faces of Billy Milligan on Netflix this week. It set my brain on fire about Dissociative Identity Disorder (DID) (previously called Multiple Personality Disorder).

For there to be a disorder so distinctive that a large portion of psychologists are skeptical exists is fascinating.

My mother had a friend who was diagnosed with DID. Maybe you or someone you know has been diagnosed as well. It's hard to deny the reality of it when you witness the switch of personalities first hand.

My mother's friend was a victim of horrible cruelty when she was a very young child, and the result of the trauma was, apparently, the split. Certain events would trigger her, and then - boom. Enter new personality.

All of the personalities we ever saw were harmless. One was a fifteen-year-old boy, and when he would come around, her children would need to find alternate rides to places because she was no longer old enough to drive.

So, from that experience, I'm strongly inclined to believe it exists. If it doesn't exist, what the hell was all that?

And then there's this strange bit: instances of DID cropped up in large numbers in the seventies, eighties, and even into the nineties, and then they just sort of disappeared.

That fact makes it seem more like a social construct. An illness of suggestion. A clinical fad, even.

But that doesn't square with my mother's friend. The timing does, but I wasn't looking at a woman participating in a fad. I was looking at a broken woman who tried her best not to suffer in that way.

In the documentary Crazy, Not Insane, we chip away at this even further, mostly with regard to killers who are diagnosed with MPD (now DID). The theory presented is that essentially every serial killer suffers from DID. That element of "he seemed so normal" or "he could never do that" that we always hear could be explained away like that, at least. Maybe his core personality was normal or gentle.

Or maybe the common element of these serial killers is psychopathy, not dissociation. Psychopaths are happy to lie, and the DSM (Diagnostic and Statistical Manual of Mental Disorders) isn't hard to get ahold of. Sure, blame your acts on an evil alter personality. That's a sure-fire way to offload your responsibility. Yes, it's still a part of you that did it, but it's not your fault, right? You can't help your (faked) disorder.

This seems like the most sensical explanation to me when it comes to people who kill for sport. And if DID does exist, faking as if you have it to gain sympathy and avoid consequences is even worse.

So, how do we ever come to a conclusion about all of this?

No, really, I would love to know. If you have an idea, please pass it along. I'll just be chewing on it in the meantime.