Tired can be a consequence of depressed, or many other things, so this could be an indirect (even cyclical) reaction.

I'm a tad bipolar. When I have an angry manic the cause is direct, but when I have a "happy manic" that lasts for an appreciable time angry is soon to follow too, I think mainly because I can't sleep well in that state. When I'm down I sleep, in fact sometimes practically hibernate, but it often isn't useful/refreshing sleep so again anger comes from that.

True ... Also depression often causes sleep problems resulting in tiredness.

I'll second this. I put myself in a downward spiral from bad sleep and being dependent on caffeine. I'm now aware of how I "feel" when I'm just really tired.

Indeed. I wanted to comment that sleep apnea can also cause irritability.