I agree no one knows "the full extent", and I do not think we ever will. A lot of information is out there though - available as far back as the late 80s. A lot of this came out when Harold Blauer's [0] sued the U.S. government [1] for testing drugs on him without anyone's consent when he was institutionalized for depression. The drug tests were covered up for 22 years...

I'm happy to see some headlines to hopefully inform some more folks, but you really have to go digging for this stuff intentionally to get to juicy details. If you are interested in doing so, I recommend picking up Weiner's "Legacy of Ashes: The History of the CIA".

[0] https://en.wikipedia.org/wiki/Harold_Blauer [1] https://apnews.com/2e5220ecb195844edacfbffdb0a37a5a