I had my adult diagnosis's with in the first 3 sessions (course my sessions were not weekly. I had a couple sessions then referred for diagnostic evaluations then the psychiatrist, therapist and I met again after all the tests have been done. I dont count the testing appointments as therapy sessions due to it was a psychiatrist not my therapist and no therapy was done just testing.). so Appointment with my therapist wise it was 3 sessions. spaced out over the course of a month.

here in america you can get a diagnosis just by asking your treatment providers for a psychiatric evaluation for diagnostic purposes. here in NY when someone requests a psychiatric evaluation a referral is put in by a therapist or medical doctor. then the client goes to a psychiatrist or psychologist and completes a battery of tests. some diagnosis's require the medical doctor ruling out medical problems. after the tests are complete the client receives their diagnosis. how long it takes depends upon scheduling and what tests need to be done.