I agree with Christina~ I think this is a chicken/egg thing. It's always hard to say what comes first. Did a trigger cause an episode or did I respond to that trigger in a certain way because of my mood/current brain chemistry. I lean towards thinking that it originates in my brain first and I respond to external stimuli based on my mood. It really irritates me actually when someone implies that I must be depressed or manic for a REASON...like, hey...the reason is that I'm BIPOLAR.