Perhaps when the body's chemicals are out of whack, one becomes more susceptible to external happenings and then it would appear as if your mood swings are in fact a response to an external. For me, I can almost always pinpoint the trigger for my lows, which are generally the result of an some minor annoyance, inconvenience or misunderstanding in my daily life.

I'm hoping some renewed cognitive work can lead to better recognition of these incidents when they happen so that I am capable of dealing with them immediately and not three days and many glasses of wine later.