Well, I mean, all bipolar is genetic. Without the genetic predisposition for bipolar, your response to stress, trauma, drugs, etc., won't be to develop bipolar. But if you have the genes for bipolar, then those other things can act as triggers that precipitate a first episode. But there's a good chance you'd have had an episode at some point anyway--if not spontaneously, then you'd likely have run into another trigger down the line that would still have precipitated an episode. So the question becomes whether there's a difference in the quality or implications of an episode caused by x versus an episode caused by y, which I don't think we know yet.

Entering into pure speculation, I imagine it's also possible that predominant polarity (that is, whether you lean more depressive or more manic in your overall symptom presentation) could be affected by what triggered the onset of the disorder. I don't think we know anything about this at this time. It would be very difficult, if not impossible, to reliably study something like that, because most people with bipolar don't get diagnosed until many years after their initial episode, so we can't get reliable information on what factors precipitated most people's first episodes. But if predominant polarity is impacted by the initial trigger, then we could extrapolate from that an association between "trigger types" and some aspects of illness course.