I am 100% sure there are proper studies of this out there, but of course I'm far too lazy to look. :)

The main reason I speculate that the actual incidence is increasing is that the diagnostic criteria for these types of disorders is actually more strict than previously. Rather than just "being anxious", the DSM now requires that the issues actually affect your quality of life.

I personally think that to a large extent, the increase in diagnoses can be attributed to the pervasive existential angst a lot of people have in 2017 (as noted above) combined with the fact that the criteria are vague enough that anyone could convince themselves and a PCP that they meet them. While I wouldn't normally mind - the psych meds do actually increase quality of life for a lot of people, which is a good thing - having accidentally withdrawn from my meds a few times, I do worry about the impact on society of a sudden lack of availability with so many people on them. I also think it tends to encourage the "me and also my brain" way of thinking about the self ("my brain" as separate from "me"), which I don't believe to be helpful.