I don't think a therapist is the best at diagnosing bipolar, although they can suspect enough to suggest you see a pdoc for confirmation. In my case, I was diagnosed as a result of taking an anti-depressant that caused hypomania. I have argued that I don't have bp because it was caused by medication, but I guess that's one way people find out. Now, I can't take AD's without a mood stabilizer or I go off the rails. My moods are independent of anything happening real life, but they can be made worse by stressors.