eli5: How does stress cause physical health issues?
In: Biology
All stress has a physical aspect – adrenaline and quicker heart beat, among other things, to make us more alert and effective at handling whatever stresses us, be it a lion chasing us or a deadline.
That’s good, but our bodies and organs aren’t made to work on that level for long, and it wears out. Wear and tear is more common at that level of activity, and you give it no chance for a rest to “repair”.
There are many connecting points.
Under adrenaline response your muscles are privileged in terms of energy usage (so you can either fight or flight). That means other systems are underprivileged, including the immune system. So if you spend more time under adrenaline surge (stress), then your immune system is at lower privilege for a longer total time, giving more chance to infections or cancers to emerge. This is kind of an indirect effect though.
A direct effect is that high stress levels lead to glucocorticoid release which is has a downregulatory effect on immune cells. It is probably just a side effect as this is a steroid hormone and a lot of steroids have such effect on immune system. Glucocorticoid hormone has its primary effect on metabolism but directly knocks down the immune system.
Elevated heart rate under adrenaline response is per se hurting your cardio vascular system.
from an evolutionary standpoint chronic low amounts of stress for months on end wasn’t really a thing. Stress was when a predator was chasing you so your heart rate ramps up so you can get ready to escape or fight it which will be over in a manner of minutes, not months or years at a time the way we see stress today.
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