My therapist was the first one to suspect it. I had recurrent depressive episodes and was having a major one when she started reading her notes and realised that only one week earlier I had felt like I was on the top of the world and now the exact opposite. She went through those notes and saw a pattern which looked like bipolar disorder to her. She contacted my doctor and I was diagnosed with cyclothymia.

A year later I got manic, at first it was just increased creativity and talkativeness, but then it leaded to me wasting all of my money and engaging in risky behaviour. Well it didn't get too bad before I landed back on earth (after 6 or 8 weeks) and went into the deepest depression I had ever had. I was unable to continue my studies, unable to take care of myself, and at some point I realised to seek help and got hospitalised due to a severe depressive episode and diagnosed with bipolar (by a different doctor).

But yes, my therapist was the first one to notice the elevated mood, that was nearly every time followed by depressive mood of some degree.