It is very common actually for people to be diagnosed with major depression and then go manic, which is how they discover that it is bipolar and not depression. The reason is that usually in mania/hypomania people don't seek help because they feel good, especially if they've been depressed for a while. We recently had a patient who had a depressed psychotic episode and went to the hospital. They put him on antidepressants and four days later he was in our office over the moon with happiness and full of plans, ideas, full of energy and elation. All I could think was "oh no... ." We had to inform his psychologist.

I was depressed through my childhood and teen years far more than when I was happy, so at 18/19 when I went manic with psychosis I thought I was "cured" or had overcome depression. I had no idea I was having a major psychotic episode that lasted about five years. So, of course I didn't seek help at that time although I really needed it, because I felt happy and good. (And at the same time although everyone around me was well aware of my delusions and hallucinations, no one did anything.)