[nafix]

Seems pretty straight-forward. Empathy requires energy and if someone is under stress, they generally have less energy to worry about others.

[tomatowurst]

I wonder if psychopathy/sociopathy/narcissism is the result of pro-longed inter-generational stress and isolation. Someone growing up say in a war zone and being exposed to violence constantly from a young age would be adapt to shut down empathy.

[goodpoint]

This is a very well known fact is psychology.