Greg referenced this article by Paul McHugh (former psychiatrist in chief at Johns Hopkins) on the show Tuesday, and it's worth posting an excerpt here, as well:
[P]olicy makers and the media are doing no favors either to the public or the transgendered by treating their confusions as a right in need of defending rather than as a mental disorder that deserves understanding, treatment and prevention. This intensely felt sense of being transgendered constitutes a mental disorder in two respects. The first is that the idea of sex misalignment is simply mistaken—it does not correspond with physical reality. The second is that it can lead to grim psychological outcomes.
The transgendered suffer a disorder of "assumption" like those in other disorders familiar to psychiatrists. With the transgendered, the disordered assumption is that the individual differs from what seems given in nature—namely one's maleness or femaleness. Other kinds of disordered assumptions are held by those who suffer from anorexia and bulimia nervosa, where the assumption that departs from physical reality is the belief by the dangerously thin that they are overweight….
Psychiatrists obviously must challenge the solipsistic concept that what is in the mind cannot be questioned. Disorders of consciousness, after all, represent psychiatry's domain; declaring them off-limits would eliminate the field….
We at Johns Hopkins University—which in the 1960s was the first American medical center to venture into "sex-reassignment surgery"—launched a study in the 1970s comparing the outcomes of transgendered people who had the surgery with the outcomes of those who did not. Most of the surgically treated patients described themselves as "satisfied" by the results, but their subsequent psycho-social adjustments were no better than those who didn't have the surgery. And so at Hopkins we stopped doing sex-reassignment surgery, since producing a "satisfied" but still troubled patient seemed an inadequate reason for surgically amputating normal organs.
It now appears that our long-ago decision was a wise one. A 2011 study at the Karolinska Institute in Sweden produced the most illuminating results yet regarding the transgendered, evidence that should give advocates pause. The long-term study—up to 30 years—followed 324 people who had sex-reassignment surgery. The study revealed that beginning about 10 years after having the surgery, the transgendered began to experience increasing mental difficulties. Most shockingly, their suicide mortality rose almost 20-fold above the comparable nontransgender population. This disturbing result has as yet no explanation but probably reflects the growing sense of isolation reported by the aging transgendered after surgery. The high suicide rate certainly challenges the surgery prescription….
At the heart of the problem is confusion over the nature of the transgendered. "Sex change" is biologically impossible. People who undergo sex-reassignment surgery do not change from men to women or vice versa. Rather, they become feminized men or masculinized women. Claiming that this is civil-rights matter and encouraging surgical intervention is in reality to collaborate with and promote a mental disorder.
Listen to what Greg had to say here (starts at 1:24:40).