Hi Blondee71,
I can't actually know what it is, but I do know that PTSD has a lot of effects within the body. One of the things it can affect is breathing, so perhaps that could be linked with the loud hiccup as I think there can be a link between the two? I have experienced chronic shallow breathing with PTSD, like I am almost not breathing at all. I was like this as a baby apparently which I think would have been to do with my traumatic birth and the events that followed. I've had two sleep studies and they both showed I have many hypopnea events throughout the night where my breathing becomes extremely shallow and very limited. You could look into doing some somatic work with the PTSD if it resonated with you which can sometimes help to remedy these kinds of dysregulations in the autonomic nervous system that come from trauma and see if that fixes the hiccup issue. I have done something called Somatic Experiencing which has helped alleviate a number of things and greatly improved my very restricted breathing. But it's very important to find the right practitioner with that kind of work as it is about trauma processing and having a good sense of safety is important. Sometimes there is an unresolved process in the body that never got to complete at the time of the trauma and this therapy allows that completion (e.g. a thwarted fight-or-flight response gets to be completed). But the hiccup you experience may be linked to something else, so just throwing those thoughts out there. You can try mentioning it to your GP to see if they have any ideas.
Just doing a quick bit of research now, I read that a stressful event can cause the diaphragm to spasm which can produce a hiccup. This is because the sudden contraction of the diaphragm causes you to take in air and your voice box shuts off, causing the hiccup. if you have quite strong stress responses because of the PTSD the effect could be quite strong in your body.
Anyway, hope you can find an explanation and solution in your case. All the best,
ER
