My personal take is this; one either has the capacity to be multiple or not - very likely it’s a spectrum. But being able to dissociate under stress is very pro-survival. One of my favorite examples is having to deal with things that would ordinarily make you puke uncontrollably or run screaming.
One thing that makes us want to change the channel instantly is when a plot is driven by some muffin that is in a life or death situation and cannot or will not dissociate enough to cope - for one tedious example, we have to jump off that cliff into the water in order to avoid the deadly threat that will get us in thirty seconds - have your moment of drama LATER!
Or for a real example;
“Huston, we have a problem,” instead of the more dramatic, “OMYGOD, WE ARE ALL GOING TO DIE!!!”
(Actually, most people do dissociate in life/death situations; we culturally ASSUME panic to be normal, but in every case where panic would have been expected by screenwriters and desk-fronted thinkers, no panic at all has been reported.
Compare “Towering Inferno” with the very real events of 9/ll - panic did not occur. People made pretty darn good choices and as a result, far more people survived than anyone would have thought possible. But at a very high price, in terms of delayed effects.
Multiples can do that normally, and do it for years without breakdown, given that their “operating system” allows it to occur in a functional way.
You will find multiples thought professions where this sort of thing comes up all the time; ER wards, EMT’s, even on the police force.
That’s because our way of dealing with stress is more adaptive to the need - we do stress out, but we can put it off until later. And we can cycle to relieve stress during the day; it’s a shared effort.
But nonetheless, everyone has a limit, and in childhood, if we are abused that can easily happen. That tends to disorder us (often in a very literal sense) in ways that are quite different from singletons. And since the medical model folk only see disordered multiples they have unfortunately leaped to the conclusion that the multiplicity IS the problem.
Systems such as ours should be a counter-example to that; we have been subject to abuse, and it’s certainly affected us, but on the whole it seems most likely that are multiplicity became explicit to deal with our also being on the Autistic spectrum.
We test out as being pretty classically Asperger’s Syndrome - no official dx, don’t have a need for one. But there are many sources for the diagnostic criteria, and several different angles to look at it; it’s pretty clear that is what we are, as closely as anyone could peg it.
THAT affects us far more than multiplicity, and our usual reasons for switching have to do with aspy stuff these days.
Sure, multiples can paddle up De Nile farther than most folks; none of us are immune to such things, and our denial can be expressed in pretty odd ways - at least compared to Norm, the Average Person.
But the way we do it isn’t the issue; the issue is that we have something to deny.
Now, if I were a sociologist or something of that sort, I’d be keeping this idea for myself until I got the relevant grants; but since I’m not and statistical analysis makes my teeth itch, I’ll throw it out.
There are a number of conditions that are exploding, indeed, have increased, possibly exponentially in their diagnosis over the last thirty years. Multiplicity is one of them; so are autistic-spectrum disorders, ADD and ADHD come to mind; I’m guessing the same is true of Borderline Personality Disorder and a few other things.
With most of those things, once you start talking about it, there is a degree of skepticism from the rest of the world; why is it only happening in the United States? Is it real, or is it a phenomenon of the diagnostic process?
The latter may be true to an extent; our insurance system is to blame for much of it in some ways, but to a greater extent, my gut tells me that it’s a byproduct of stress.
And I should point out that while Alvin Toffler did not predict this exact situation in Future Shock, to the best of my recollection, he did indeed predict that Stuff Would Hit The Fan, and I believe he predicted a rise in mental disorders and stress-related physical conditons.
The US is particularly affected because of a number of cultural conditions and of late, hugely increased pressure on individuals.
This is compounded with a whole number of things that amount to a fog of shared background anxiety; access to medical care, worries about finances in a climate of regulation and provision that requires that everyone be their own CPA, fears of war and terrorism, the complete loss of job security across the board - most people are far, far more stressed than their parents.
Other countries have done a far better job of dealing with these collective stresses and fears, but here, that’s “Socialism” and so it’s rejected, or hideously over-complicated in the name of “privatization.”
I’m sure everyone can think of other examples; one only has to listen to talk radio to get a feel for the visceral fears that lurk in Middle America.
Now, couple that with another phenomenon that is the indirect result of two world wars; Urban concentration and a huge increase in college education.
That’s a good thing, of course; but what it does is concentrate all the people who can pass an entrance exam in situations where they will meet, fall in lust and breed. 
People that in other situations would probably never meet someone quite as smart as they are fall in happy geek love and breed 2.5 little geeks.
This, and other concentration patterns have resulted in Asperger’s having the alternate name of Silicon Valley Syndrome.
So aside from the social stresses, we have been breeding for many of these traits for at least two generations. Of COURSE there’s an explosion!
My wife has a great little saying; “Different does not mean broken.”
I know that over my lifetime, 80% of my problems were not internal; for the most part, I worked just fine. It was the reaction of other people to my differences that was the problem.
I know a lot of folks will be horrified at the idea that conformity is not a sustainable ideal. There are folks that think we should all look, talk and think exactly alike, and as that’s sort of a cultural Meme here in the land of supposed sacred individuality, it’s not publicly recognized as being dysfunctional.
But it is; since things that make you treat other folks in appalling ways for reasons that don’t bear up under rational examination are, by definition, nuts.
Now there’s some denial for you.
