I was actually a participant in a follow up study that I read about on Hacker News about a year and a half ago. Thanks to whoever posted it I haven't been able to find the HN post since then.
Just to confirm what Alex3917 said, they did ask us to follow a meditation program before the first of either 2 or 3 sessions(I ended up with 3).
I don't know all of their selection criteria, but for the study I was in they were looking for people with existing "spiritual practices" and little or no previous psychedelic experiences.
Just to confirm what Alex3917 said, they did ask us to follow a meditation program before the first of either 2 or 3 sessions(I ended up with 3).
I don't know all of their selection criteria, but for the study I was in they were looking for people with existing "spiritual practices" and little or no previous psychedelic experiences.