I've suffered from this 'fight-of-flight' state all my life, overreacting to any stresses, not only emotionally but also physically, with abdominal cramping, diarrhea, increased urination, dehydration, sweating, racing heart, with any stress, every day.
True story: it all disappeared three years ago within a couple weeks of going gluten-free / casein-free.
I don't have an explanation to offer and maybe I am a unique case.