I'm certain that they are a symptom, but I am unconvinced that they are a sole cause for this
Edit: Obviously not a psychologist, but just from what I observe: People have had way higher expectations from life than ever before in the past, and life has not really been meeting those expectations.
A lot of people I know simply aren't going to enjoy the same luxury that they grew up expecting, being told they would have, that they were "promised".