I had depression for four years before I had my first manic episode and my diagnosis was changed to bipolar disorder. The main sign before my first manic episode that I was bipolar were my extreme sleep abnormalities. I'd be up until 5AM, sleep all day, and stay up even later the next night. My circadian rhythm was all out of wank. If me and my doctor could have caught this earlier I could have been trying the correct medications even sooner and I would have started getting better sooner. The reason I am sharing is so if your sleep pattern is messed up like mine was you can talk to your psychiatrist about the possibility that you have bipolar disorder simply lacking your first manic episode and have the chance to get betters years before you otherwise would have. I hope this helps at least one person!