Why would such tests have biased results?
It's not just the isolation they are dealing with. The quality of living under that circumstances is a lot worse than on a space station or on a Mars base. They don't have a lavatory or a bathroom, they don't have the best source of food supplies, they aren't there by choice, they weren't prepare for it, and on the other hand they have a rescue team trying to get them out that's somewhere out there for them all the time, while any future astronauts will be locked out with few people caring about them, and with several months of guaranteed stay, and with millions of kilometres to the rest of humanity. Only the isolation part is the same.