RatRolyPoly
There is very little research available. (That fact alone should be enough to give any medical or psychological professional pause).
There's the famous Dhejne et al:
journals.plos.org/plosone/article?id=10.1371/journal.pone.0016885%20
This one found mixed results; improvement for some and worsening for others:
www.ncbi.nlm.nih.gov/m/pubmed/26479779/
And this one I found very interesting.
www.researchgate.net/profile/Griet_Cuypere/publication/247335377_Long-term_follow-up_Psychosocial_outcome_of_Belgian_transsexuals_after_sex_reassignment_surgery/links/5a7c1468aca27233575bb713/Long-term-follow-up-Psychosocial-outcome-of-Belgian-transsexuals-after-sex-reassignment-surgery.pdf
Positive outcomes, when "gatekeeping" is used.
Our multidisciplinary gender team has adopted a cautiuous policy. We advise a dual-phase hormonal schedule, with a first reversible part in which sex-specific features are suppressed, together with the start of a real-life test. Not until in the second part, cross-hormones are given that result resulting in irreversible feminization or masculinization (T’Sjoen et al., 2000). Our data confirm that our policy is recommendable and that psychiatric counseling throughout the sex change is not an additional luxury. Even post- operative psychotherapy is sometimes needed. If there is a positive relationship with the psychiatrist pre-operatively, he or she finds it easier to return to this psychiatrist.
Do you think that the small cohort of transpeople for whom transition appears to be a total cure (such as Jaycee on this thread) are suffering from the same thing as those for whom it doesn't help? Could the key be being better able to tell between those who are truly transgender (ie transition = cure) and those who are not? Or do you think everybody could (or should?) have treatment to their mind only and never to their body?
So, we have a group of people with similar symptoms. One treatment protocol seems to help some people within that group and not others. Yes, this would suggest to me that there are different underlying processes going on. Look, say you have someone come into the ER with coughing, fever and shortness of breath. Just from the symptoms, that looks an awful lot like pneumonia. Empirically, that person would be given IV antibiotics in the ER, because that's the most effective treatment for pneumonia, and even if the person doesn't have pneumonia a dose of antibiotics isn't going to cause any long term damage (allergies will of course be checked first, before administering any medication). However, that person will also have a chest x-ray, blood work and a sputum sample sent. Because it could also be lung cancer, or an asthma or COPD exacerbation with an underlying viral illness. Antibiotics won't help that; and not effectively treating the underlying cause will not help them and could be fatal. That person will not just be given antibiotics without further diagnostic testing. Furthermore, that person will not just be given antibiotics without the docs also monitoring follow-up chest x-rays and lab work to ensure that the antibiotic we are giving them is actually helping and they don't need to be switched to a different one. Same symptoms, but different underlying causes mean different treatments. Same symptoms, same disease, but different bacteria causing the disease means different treatments, too.
So yes, differentiating between who is actually going to benefit from a certain treatment is vital to effectively treating people. This is one of the principles modern medicine and psychology are based on.
And no I don't think that people should have only either medical or psychological intervention - the more variety of treatments available, the better. The better able to offer people the most effective the better. Having treatments that are less invasive, the better. Only offering highly invasive and life-altering treatments to those who will truly benefit, much better. The better able to differentiate who will benefit from a certain treatment protocol (like the clinic I quoted in my last link) the better.
We need research. We need gatekeeping. The current push is affirmation-only with no exploring of other underlying causes is harmful. Unfortunately in the current political climate differentiating between people who would benefit from a certain treatment protocol - i.e. those who are "truly transgender" versus those who are not - is seen as transphobic bigotry.