Poor health puts definitely stress on body. Being depressed is stressful. But an environment can make one forget about the health issues, so decreases the stress.
Some people have steady cortisol. It won´t go high if they think about upcoming situations or in public places. Anxiety is also related to cortisol. And it´s vice versa. Anxiety increases cortisol and cortisol increases anxiety. Depends where to underlying cause is.
It´s all body chemistry and if one understands his/her body chemistry, one can "hack" it.