the point is that if you're depressed you're not angry. that is you're not expressing or feeling your rage and anger.
if you could get angry maybe you wouldn't be so depressed.
think about the word literally: depression (not sadness, grief, remorse, melancholy, mourning). emotions. usually negative ones. often rage are pressed down on, inhibited, depressed.
flat affect (no emotion) is a big marker for depression. you need to work out what emotions are being supressed and why.
imho