You're right to point me out that the state can actually origin in pure, causeless, anxiety. Thanks, I was blinded by the reasoning I wanted to defend. However

You're right to point me out that the state can actually origin in pure, causeless, anxiety. Thanks, I was blinded by the reasoning I wanted to defend. However I think that there could be cases where it would come from, e.g. thyroid instability. Usually nobody is monitored 24/7 on its thyroid hormone levels, etc. Could be also adrenal glands. Maybe when they are weak, or subject to autoimmune problems, their secretions can be irregular, or their reactions to stimuli can be too weak, too strong, quick or slow. Then the subject would not be anymore resilient to normal stress. That would explain why normal stress => pathological effects on some people. Then again the organ-level defects could be themselves a consequence of elevated stress during long periods, so one could raise the question about which is first of the egg or chicken...