Look up the DSM criteria for mood episodes. Absolutely nothing in there about situational issues. Rather, it's a differentiating criteria that specifies symptoms must present over a marked period of time. The specifications are very clear, and have absolutely nothing to do with external stimuli. Quite the contrary.

If you're already in an episode and your reaction is more extreme than your neighbor's that's to be expected. But external stimuli _causing_ the episode? No.