HPPD and substance-induced psychosis are very real, however I don't know of any cases that were the result of microdosing.

There's a difference between taking drugs and taking them every day, becoming reliant on them, considering we're talking about hallucinogenics here.

You think LSD induced psychosis is not a thing?

The right question is "how often does LSD cause psychosis?"

Every time you take it?

It's basically a window into a malfunctioning brain. You bounce back when it wears off, but you can definitely change from tripping too much. Have you never met someone who has done too much acid?