Pretty sure every human who understands the concept of death are stressed about it at some point in their life.
So, those who do not understand the concept would probably not stress over it. Like someone with brain damage, or animals I guess.
Who knows, maybe my cat is in a bad mood sometimes because she is having an existential crisis, but I kinda doubt it.
To supress elements in a herd? Sure it does.
Healthy for the individual? Not so much.