What if the hallucinogen has long term health effects? What if tiny people show up for a participant years from the experiment, while driving? I guess you can

What if the hallucinogen has long term health effects? What if tiny people show up for a participant years from the experiment, while driving? I guess you can be upfront about unknown unknowns, and most human experiments have some of those, but I assume there are standards to keep those to a minimum.