I also do not think thoughts are causing them. I agree with the idea that you maybe seeing the cues which can show up first in how you think. But there also is another possibility. I think events can help precipitate mania or depression. Maybe this happens when you are already pre-disposed to another episode, where your time has come for such an episode to happen. Events can have significance because of what you think of them, where you can even be unaware of these thoughts. But the event does happens first.