You're confusing the word stress. There are multiple meanings of this word in the English language.i don't think you understand what stress means
if i press my pinky finger onto my knee cap, i'm applying pressure, which creates stress...so your argument is what? my little pinky now causes male pattern baldness because...stress is always systemic, right? local pathology is arbitrary, in your own words...
The one you gave an example of would be defined as 'pressure or tension exerted on a material object'
However, the one we are referring to when talking about causing a systematic problem would be defined as 'a state of mental or emotional strain or tension resulting from adverse or demanding circumstances'.