like there is no study on this because a system without gatekeeping and pressure does not exist.
but literally every single story of transition-related regret I read is either
a) person got what they asked for but are still dysphoric
or b) person was put unter pressure to pursue treatments they didn't want
and more often than not in the b) type stories the people whose task is gatekeeping are also the ones doing the pressuring. I actually think in every single story like this that I've seen (where it wasn't social pressure) it was a therapist/counselor that did it, or their offices (like "if you don't get X treatment you cannot get further counseling")