I think situational stressors could possibly cause bipolar episodes, but you make a good point that sometimes we are just plain experiencing sadness or grief, or just a lot of excitement. As FluffyDinosaur wrote, my depressions are a bit different than just my periods of sadness or grief. They have different characteristics. If my depressions do stem from something situational, it morphs a bit. The last time I had extreme situational sadness was when my pet died this past year. A couple years before that, my family lost my nephew and I lost my previous pet. It's just horrible! Horrible! But it was different than my depressions that were clearly mental illness.

Unlike many, I do not call mood elevation "blips" episodes. People can argue with me about the DSM-5, but I do go by that when labeling episodes that I've had. Sure, some excitement can occasionally take me beyond what would normally be experienced without bipolar disorder. But if lasts only hours to one or a few days, I don't call it hypomania/mania. I call it mood lability or the "blips" I mentioned. I guess an exception would be if that one day or two was so extreme that I ended up in the psych hospital. Then I guess I'd call it an episode. Again, that is allowed according to the DSM-5. Please no rotten tomatoes for me actually agreeing with some of what's in that guide. So so often people say "I'm manic" when in reality they've had what I call a "blip". Or their moods fluctuate up and down for a few days, and they label themselves "rapid cycling" or in a "mixed episode". I guess people can label as their heart desires, but I don't label that way, for myself.