I don't currently suffer from PTSD, but I know at least twice in the past 6 years I've had symptoms of it, after witnessing a friend in an accident, and in dealing with my aunt's death.  Both times I've had counseling, but I can't much remember much of my symptoms the first time it happened (I was pretty numb).  Anyways, the second time...actually there's a bit of a back story.  I know this sounds morbid, but throughout my teen years I would 'see' corpses everywhere for no apparent reason.  I blamed it on overactive imagination and just regular teenage stress.  Now, you need to know that corpses are my number one worst fear.  I'm talking fleshy, mutilated corpses.  I still freak out when they pop up unexpectedly in movies and such, but the ones I imagined popped into my mind so frequently that I'd grown a bit de-sensitized to them.  They were usually the same guys in the same spots (hiding underneath my bathroom sink, laying in my bed, etc...)  Yeah, I KNOW this sounds crazy, but it's very similar to a little kid imaging monsters under the bed (mine are just a bit more graphic).  After I started college, the crazy imaginations disappeared, with only the occasional corpse.  But after my aunt passed away a few years ago, I know I was having a hard time dealing with it.  She passed right before I went to study abroad, so I was well distracted from her death for several months.  But about a month after returning to the US, I was having a really hard time adjusting back to my life here.  I was grieving for her by myself (most of my family had already had time to grieve while I was gone).  And that's when the corpses started popping up again.  It was getting OUT OF CONTROL.  I didn't even have to try to daydream for them to appear, they'd just magically be nearly everywhere I looked, even in the daytime they would show.  They were starting to go from being a silly over-active imaginary thing to being full-on hallucinations.  I was losing sleep, and was anxious whenever I was alone.  This was the worst it had ever been...I'm talking seeing them each time I walked around a corner, opened a closet door, walked into the shower, etc...  I knew they were just hallucinations, and after the initial shock of seeing the corpses each time they appeared, I was able to go one with whatever I was doing (though I remained distracted and scared).  And when I started to 'feel' them touching me, I decided it was time to see a counselor.  After a few sessions, we got some answers down.  I think she termed it delayed-grieving??  I was well aware that they were hallucinations; schizophrenia was very quickly ruled out.  It was grief, in addition to reverse culture-shock (from returning to the US) and just academic/relationship stress in general that started all these PTSD-like symptoms.  Eventually I was able to find closure from my aunt's death and the hallucinations stopped.  I haven't had any 'episodes' like that since, but to this day, I still don't know why I get such specific and morbid hallucinations.  If I were to be pushed onto the edge like that again, have some strong emotional disturbance, I wouldn't be surprised if the hallucinations started up again.  Even though they don't 'pop up' anymore, I can very easily imagine what the corpses look like.   But it's probably better to just leave it alone for now.  I'm not gonna go poke the embers of a fire that's been put out.  

Ok, so to answer the post, I don't think PTSD affected my MD.  I've had MD all my life, since I was a kid.  But my first real diagnosis of PTSD was in college, when I saw my friend get into an accident.  And the second time it happened, I think my MD kinda fueled the hallucinations and the PTSD (so for me it went the other way around).  Since I can so easily let my mind wander without me knowing it, I think it's even easier still, for my subconscious to bring forth unwanted thoughts and feelings, especially in a time of stress or after some sort of trauma.  I think, if I didn't have MD, I wouldn't be so susceptible to the PTSD hallucinations.

Yes, PTSD is probably a very large contributing factor to my DDing. Due to all the trauma I've gone through(being molested, severely neglected, and raped) I've kinda ended up pretty far down my rabbit hole at times. I can understand how something that traumatized you can end up playing a role in your daydreams. Some of the stuff I have gone through has seeped into my worlds and has become a main event that often my worlds are built around just to cater to it. I don't mind and still enjoy them. I think that it is a good start to overcoming the trauma. Because it can help foster a sense of control that had previously been taken.

I've daydreamed immersively since I was a kid and I don't think that in itself was bad, but because of traumatic events and personal problems it did become a coping mechanism. 

I won't go into the specific traumatic event(s) I experienced, but something I have done is daydream about emotionally overcoming them and/or playing out very exaggerated events related to overcoming them. What you said above about afterward you would feel terrible, I felt terrible afterward as well. Yet I would return to daydreaming about it, and do it again, over the years. Maybe I was trying to deal with and process the trauma because it has never been resolved, and I might never be given the answers I need as to what happened, so in my mind I created a scenario of overcoming and getting the answers I need for peace. 

Like I said, I feel terrible afterward so I don't like it when I daydream about this. So now I try not to, but sometimes it just happens. Like a reflex? Because I wish for peace so badly, how can I not dream of it? Yet it is vicious cycling, because I am never satisfied, because it is not real. It is a dream.