MDD is the "bread and butter" of psychiatric practice. I'm not really sure how much that's changed over decades. Of course, depression treatment options have evolved greatly since the late 80s, truly a blessing.

You're probably right that increased awareness, reduced stigma and improved attention to diagnosis play a role in apparent population rate increase. Interesting how the comments here put forth quite a few "theories" regarding sources of the increase.

AFAIK there's no definitive explanation of the observation. In passing we should note that many other psychiatric conditions have parallel rising incidences. The factors you cite apply to those conditions as well.

Psychiatric conditions in general are very complex, with associations to a wide array of factors. Most likely many small contributors add up to vulnerability to one or more of these conditions. Our brains are constructed to prefer lumping things into simpler categories. What we call MDD clearly enough is not a unitary disease but outcome of a messy set of myriad "causes" diagnostically lumped together.

The progress made in identifying and treating psychiatric disorders is impressive and gratifying. The more we accept the messy reality, the greater the level of progress we'll make.