Most basically... Neither does either.
You're missing some interim steps. Which is what I suspect is what you're actually interested in. It's kind of like saying "What about being American makes people obnoxious?" Or fat. Or smile all the time. Or whatever. It doesn't mean (some) Americans aren't obnoxious. It also doesn't mean that there aren't contributing factors to those issues. Or what about being Australian makes people drink beer? It's just that it's not a direct / causal relationship.
First off, nuts & bolts:
https://www.myptsd.com/threads/understanding-post-traumatic-stress-disorder-ptsd.86476/.
"Simple, to the point, no bullshit breakdown of PTSD for both the sufferer and supporter.
"
So what are some of the interim steps that
can add up to infidelity? (Or violence. Or drug use. Or any of the other paths that some people with PTSD tend to walk down, but hardly most, much less all, because they're not direct symptoms.) These are big issues with lots of moving parts. What follows are just a handful on each to get an idea:
- PTSD aside... Rape victims
tend to split into 1:2 camps: Cut off from sex, or very promiscuous. (Again, tend. Many don't split into either camp, but those are the two big 180 degree different trends.) For those that slip into promiscuity, there tends to be several more camps, and not everyone falls into them (notice the ongoing theme? ;) ) Reclaiming sex, control, power, revaluing sex (up or down; people often fall into the trap of thinking people devalue sex, but it's as often the other way around), erasing bad memories with good ones, faith in humanity (up or down, again), retraumatization, punishment, fear/proving yourself, the list goes on.
If your wife fits into any of these categories, or others, would be things to work out with her. Or not. It often takes quite a bit of therapy to figure out all the little facets that go into
why someone is doing something, and why is often secondary to ceasing & desisting. Sometimes why is helpful, sometimes it's not.
- Another common trend of rape victims is pristine vs dirty (my own words, I wouldn't use them with someone else unless you're prepared for some massive rage. The whole "I can call myself XYZ, but no one else had better"... Especially because -again- this is only a trend. Not everyone does this.). Meaning they
do not want (to the point of it feelin like a need, instead of a want) to bring in all the "dirty" into something they view as healthy/ pristine/ special. It's a form of compartmentalization. They want to keep the good parts of their lives from being "contaminated" with the bad parts of their lives. Often leads to a lot of pain, because the disconnect is the common denominator: Yourself. You live in both worlds, so both worlds are affected by what you do in the other. Lotta denial in this one, usually. To the point of "I would rather divorce you, and keep you clean/special/safe in my mind, than infect you with all the dark that lives in this other portion of my life". Neither compartmentalization, nor that particular argument, is something unique to rape victims. Cops spouses & military spouses are on the receiving end of this one a whole helluva lot. The bone deep
need to keep 2 worlds separate. It works until it doesn't. And then it usually fails in a pretty spectacular way. When worlds collide? In a relationship divorce or a breakup is more common than moving past it. For too many possible reasons to list.
The above hasn't even touched the PTSD side, and is only the tip of the iceberg on rape psychology. I'm going to go ahead and stop, here. Because this is probably more than enough to see
why therapy has helped. People can spend 8 years in school studying this stuff, &/or a lifetime recovering from it. It's complicated. And
none of it may apply to your wife. But you asked an incredibly broad question, so... Shrug. The easy answer is that your premise is wrong. Neither causes either. But if you go beneath the surface? Yeah. Lots of moving parts. Which can
definitely contribute.
If you want to know more... I really suggest the article linked above, and working with your wife & her therapist. They know the moving parts that are applicable in your own lives.