Cancer is not the best example here. Cancer, like anxiety or depression, is not a single disease, it's cluster of symptoms that can have a multitude of differen

Cancer is not the best example here. Cancer, like anxiety or depression, is not a single disease, it's cluster of symptoms that can have a multitude of different causes. You can tell when it's bad enough, like if there are visible tumors, but try to get 3 doctors to correctly diagnose whether a cancer is completely gone after treatment. On the other hand, I guarantee 3 out of 3 doctors will diagnose my panic disorder as panic disorder. I have recurrent tonsillitis, clearly a physical disease, yet 3 doctors couldn't figure out the cause. When it comes to disease things are almost always murky, whether it's "physical" or "mental".