I knew for sure. I enjoyed psychology and thought my symptoms seemed similar to the stories of people with bipolar disorder. My initial dx at age 18 was major depression and ADD. I was medicated with an SSRI and methylphenidate. The combination worked for a while and things seemed to get better and better until I became manic. The doc took me off the stimulant but didn't diagnose the bipolar, instead figured I was abusing the stimulant. I didn't do very well on the SSRI alone so eventually stopped taking it. I stopped seeing the doc and continued to cycle for a few years. I eventually ended up in a mania so severe my family friends and coworkers were expressing concern. Someone called the doc for me and family and friends stayed with me until I could get in to be seen...even though they were afraid of me.