I also believe there is a genetic factor but for some people it requires a trigger. Or maybe everyone requires a trigger but since we're all different, the trigger is different. So, some can get triggered early and some later. Like for me, maybe I got triggered as a kid (because I bet I had it as a kid,) because a) my mom was dying of cancer, b) I was severly bullied throughout elementary school until late high school, and then lesser bullied until my late 20s....

My dad has depression and my mom had some type of nervous thing and was a horder (so was her mom,) and my dad's first cousin has schizophrenia. So, I think it's in my bloodline, even if not everyone had it manifest as BP. I also believe in the idea that mental illness is a spectrum, not just an all or nothing thing.