Dear Dawn (and all reading this thread) ....
I was thrilled to read your response to this thread. You were spot on with your advice, so helpful in your specificity.
To anyone needing such a letter, the psychiatrist, psychologist, family doc, whoever, should state that you have a need for an animal as not just a companion for emotional support, but in order to enable you to function closer to normal and cope with your condition.
It is not needed to name the particular diagnoses you have, but I have no problem (personally) with that as I am a strong advocate of the emotionally challenged

and "out myself" all the time. My family of origin advocated "hiding the shame and embarrassment", and that does none of us any good in dealing with societies issues with us.
My doctor just said that I had "psychiatric conditions" (C-PTSD, bipolar 2 & ADD) and that I needed my current pet to attain a higher level of functioning, and he specified the various behaviors and emotional conditions my dog helped. At the time, I was a bit uncomfortable with all the detail, but when your doc can agree with you that your emotional/mental health has/is improved by the presence of your dog and be willing to help you verify that for the purposes of housing and reasonable access, then it carries significantly more weight.
I carry my letter with me when traveling by plane, and when visiting friends who live in restricted housing (ie, condos), and I take it in to post offices, doctors offices, public places and IF I am confronted with a negative response, I can drag it out (I keep it protected in a plastic sleeve). Only a hysterical shop owner or a park attendant threatening to call the police can make me decide to leave - life is too short to deal with every single one irrational close-minded individual.
OneMoreTime