To me it read as it being part of an episode (whether up or down, though more likely up, but in an irritable way as opposed to elation, which to me seems like "happy hypo", if that makes sense). But the within an episode thing is important.

If it's a regular state of affairs/recurring theme, it's not likely BP-related. That's actually a decent way to try to suss it out.

(Also that one needs to consider substance abuse when trying to determine a source.)