The reason for failure to thrive other than insufficient nutrition, can be suppressed growth hormone secretion due to emotional neglect. In the following example, both the emotional neglect and insufficient nutrition were combined, though:
Psychosocially stunted growth masked as growth hormone deficiency, (Klinische Pediatrie, 1999):
Short stature is a ...
The fact that positively-reinforcing is causing a self-fulfilling prophecy, the second one seems like the observer-expectancy/Rosenthal/Pygmalion effect to me. There could be a more particular form of it but generally, I think it fits the scenario.
The name comes from the famous Rosenthal-Jacobson study:
Rosenthal, Robert; Jacobson, Lenore (1992). ...
Interestingly, the authors appear to have been aware of your concern:
Given that the only difference between these groups involved a subject
variable for which there could be preexisting differences in DTA, we
included a third group of creationists who read a nonthreatening
Since the evolutionist/anti-creation and creationist/control groups ...
TL;DR: Multiple approaches have been tried over many years. Current medical evidence strongly supports an "affirming approach" to alleviate gender dysphoria. "Corrective approaches" are considered unethical, and withholding treatment is not considered neutral. It's explained in the referenced AAP slides, e.g.:
Children rejected and not supported are at ...
I have found 2 papers that may be relevant to your question -
This paper probably answers your question the most - I have only schemed through it, and it seems that the results were insignificant. You can check out the paper in more detail, hopefully it will get you to more resources that can help with your research.
I have also found this paper which ...