in our household we treat all overly broad, trendy statements like this one with a huge grain of salt
the difference between rates of diagnosed major depressive disorder (MDD) vs the past has much more to do with a combination of the diagnostic criteria being refined [1] over the years and the increase of screening [2] during your annual checkup (something physicians were recommended against doing as late as the 90s). you know how your PCP asks you now how you're feeling, if you've had thoughts of self-harm, had any loss in appetite, or have given up your hobbies? that's the one
if you need to blame it on a social trend, there's a sharp correlation between the rates of suicide in the USA [3] with the transfer of wealth from the bottom 90% of people to the top 1% [4]. as they say, correlation is not causation but it is one of the best indications that it might be. smarter and much better trained people than I can probably do the in-depth research and analysis needed to make that claim
[1] https://www.ncbi.nlm.nih.gov/books/NBK519712/table/ch3.t5/ [2] https://pmc.ncbi.nlm.nih.gov/articles/PMC3291670/ [3] https://www.cdc.gov/suicide/data/index.html [4] http://blog.oxfamamerica.org.s3.amazonaws.com/politicsofpove...