I agree mental health does affect physical health by quite a bit/
I remember having a casual social conversation with a woman who worked as therapist a few years ago. She told me her anxiety patients on average look about 10 years older then there actual age. So anxiety does age you prematurely. She said thats why is very important to learn to manage your anxiety in a healthy way (not with drugs or drinking like a whole lot of people do to cope)
The thing its very hard not to feel anxiety, especially when someone is already prone to neuroticism due to genetics. If its encoded in the genes then its something beyond my control.
Like most people said anxiety is an irrational illness, its very hard to rationalize it if it keeps making up false scenarios (hence why its a life long illness for lots of people)
But now a days everything kills you lol.
Regardless, social anxiety existed even back in 400 BC.
Literary descriptions of shyness can be traced back to the days of Hippocrates around 400 B.C. Hippocrates described someone who "through bashfulness, suspicion, and timorousness, will not be seen abroad; loves darkness as life and cannot endure the light or to sit in lightsome places; his hat still in his eyes, he will neither see, nor be seen by his good will. He dare not come in company for fear he should be misused, disgraced, overshoot himself in gesture or speeches, or be sick; he thinks every man observes him
It could be a trait that was passed down through genes, but maybe the body adapts itself to high stress