coping with dark humor

I don't know quite what got me thinking about it, but I wonder about its relationship to pain and suffering. I remember hearing in passing before that it was a thing among holocaust survivors, which is an extreme example, but shows how it can arise as a coping mechanism.

Liberal me would probably say that outside of such extreme circumstances, dark humor is just a sort of humor preference and doesn't necessarily mean anything on its own. But I'm not so sure about that in reevaluating it.

Is it ever "just humor"? Or is dark humor specifically tied to pain? Should it be taken as a kind of canary in a coal mine sign of suffering in people, even when they otherwise act fine on the surface?