This may be a long shot, but just curious if there is, perhaps, a commonality with this like there has been with so many other things among us all.
Do any of your ADHD partners often get sick/or are often just always feeling a bit "off"?
My ex-BF seemed to be sick so often (it was long distance so obviously hard for me to ascertain). He very often had headaches, heartburn, felt foggy...he caught colds easily and often had stomach issues. He also had a sleep disorder and if able, would often sleep for 12-16+ hour stretches.
He also smoked and refused any suggestion of mine to potentially make himself feel better in any way...citing genetics for his weak immune system, the famous "this is just how I am" line, while at the same time denying he could possibly die from lung cancer like his father had because he believed his dad was exposed to issues at his job in a factory, not because he also smoked heavily.
Anyway...just more curious than anything to see if the sick thing is common...