Triggers can bring on various types of episodes or anxiety and can be negative (like uncomfortable stress), positive (like something exciting in a happy way), or seemingly neutral (like more sunlight than usual). Situational depression is pretty much the same as the negative trigger, but usually a result of a circumstance or event and is always leading to depression. I think that on some occasions, negative triggers can even cause hypomania or mania as odd as that sounds. Maybe examples could be jet lag, alcohol abuse, or even overwork making one elevated instead of depressed. It seems odd when sad or stressful things bring on mania, but I can say it's happened to me. Maybe the mania is then mixed or oddly euphoric, which seems surprising. Then there is depression caused by a switch from mania (even euphoric mania). That seems to me to be sort of situational or even neutral in a sense.