You don't need to be very smart to get existential dread from "climate change will kill us all and I can't influence much", "the upper class can still fully rule our lives" or "at some point, someone will create an AI that might kill us and there's not much anyone can do about it". Even someone hardly qualified to work at McDonalds can think that, usually in addition to "I can never handle a job to get a living wage", which I'd actually consider to be more serious downers on ones happiness.