Biologically speaking, it is a trait that makes you aware of danger, and therefore more likely to avoid it. But in the modern world, the negative headlines don't help us avoid danger.
In fact, the depressing news drags us into the biggest danger in the modern world.
Listening to the "everything sucks" headlines and articles does one of two things:
1. It leads to stagnancy and inaction by selling a victim mentality or a why even bother philosophy. It leads people to believe that things are out of their control, and there is really no point in trying. Why bother when whatever elite group will continue to oppress whatever minority I am part of? Why bother when it is rigged against me?