How do you know only humans have this problem? Sure, you never hear other animals talking about this kind of thing, but they also, y'know, *can't talk at all*, so that doesn't necessarily mean anything. Unless... oh shit, you don't think you've been talking to animals, do you?

A human who thinks they actually *have* a fish body, with gills and everything, would indeed be suffering from psychosis. A transgender person, however, is entirely aware of what kind of body they *do* have; they're simply not okay with it in ways that can lead to profound unhappiness if not acknowledged. And treating it like a mental problem to be "corrected" is not the right kind of acknowledgement, because that's what *was* done, for a long time, and it empirically *did not work*. We may now find ourselves in a period of over-correcting for that past mistake; we may eventually conclude that some of what we're doing now isn't quite right, either; but going full-reverse back to what we did before is definitely not the answer.