Cyllya - What you say about diagnostic labels being based on symptoms/behaviors and possibly lumping together disorders with widely divergent causes is, IMO, a very, very important insight. I wish more people thought about that.

A child with a high fever can have a seizure. An alcoholic in withdrawal can have a seizure. A person with a brain tumor can have a seizure. A diabetic who takes too much insulin can have a seizure. But we don't conclude that all these persons have the same diagnosis. They may all have the same symptom, but it really matters that, in each case, the cause is radically different.

There are many people, like myself, who experience frequent, wide variations in mood. That's simply a fact, observable by others. But I'm not convinced that all of us who experience this instability of mood/affect are necessarily afflicted with the same pathology. To say my mood varies a lot because I have bipolar disorder is like saying I'm often late for appointments because I have "arriving-on-time-disorder." (which, btw, I do have.)

We have to have categories (diagnostic labels) to sort stuff into, but we ought not, IMHO, to take these categories too overly seriously.