The instinctive thought for a millennial is that this is caused by Boomers - their parenting is so atrocious that they've constantly inflicted PTSD on their children. This *might* check out - autism prevalence per capita seems to cap out around 2012. Someone who wants to follow this thought through would conclude that Boomers, Gen X, and Millennials were all collectively atrocious parents to the point of constantly inflicting PTSD on their children.

...I'm skeptical, given that Millennials are some of the most limp-wristed and fawning parents ever seen. My hatred for Boomers is immense, but the data doesn't back that up so good.