mostly diagnosis comes from a psychologist who does psychological testing or could be done by a psychiatrist who does testing. usually testing is done when there is a suspicion of a particular disorder or to rule out something. you can ask for testing or for a diagnosis from your pdoc or T.

we were tested informally by our psychologist mostly because insiders presented themselves. she had suspected but couldn't diagnose until there was presentation of an insider. then she did some testing to confirm her diagnosis.

hope this helps.
W_I