It started at roughly the time of his divorce, so it's hard to imagine there's not a connection. But, of course, you're right that we'll never know.
Not sure why we are being coy about the triggers. Society of his youth and the biology are well documented.
I don't want to excuse his opinions but that's the sort of event that can change a person.
He did online chats, and did one immediately after. It's a tough watch. https://x.com/ScottAdamsSays/status/1046764270128484352
The description of reality is not at all the same as supporting it. "Is" vs. "Ought to be".
In fact, growing up in the very affluent part of my city, I saw a bunch of kids die using opiates to mentally escape the weird family fiefdoms where they [p/m]atriarch inexplicably wouldn't ever need for money, so went completely off the rails mentally. I was prescribed a bunch of opiates (including fent) after a bad ski accident, and can tell you that they basically work by turning down the volume on life around you. I can understand why someone would turn to them to mentally escape a bad family life.
About the only good thing I can say about recreational Xanax is that those kids are generally still alive in contrast to the ones who preferred opiates.
Scott Adams put himself on a pedestal above anyone else in his comics; he was Dilbert. The only smart person in the room. He was always a celebrity obsessed with his own existence. Little difference between him and Tim the Toolman or a Kardashian.
Low effort contributor whose work people laughed at due to social desirability bias. No big loss.
But his (first) divorce was in 2014 and his blog posts already seemed bitter around that time.
Edit: as another comment points out, it was a few years even earlier than that so I stand corrected.