Its symptoms or side-effects did the harm. What seemed to unleash the deadly disease, such as living near smelly places in urban areas, didn't cause it. Cholera came from what wasn't seen, heard or smelled. The cause was hidden, a microorganism found in drinking water. In fact, it's the modern version of that disease.
Stress triggers discomfort, disabilities or worse in millions today.
It's commonly believed that most visits to family docs result indirectly from stress. It is harmless. Those are concerns related to changes in circulation, breathing and more. Like cholera, it isn't what is obvious that creates the strain. What causes it is something you don't recognize at the time.