I believe I have more than one mental illness, my anxiety also predates my Bipolar diagnosis by a month. My GAD also makes me have panic attacks, I don't think that is a component of Bipolar but rather that of my anxiety.

My PTSD is also a different diagnosis than my Bipolar or Anxiety, sometimes my anxiety makes my PTSD worse; but I still think of it as a different diagnosis. So I have three mental illnesses that all have different symptoms, sometimes one condition makes the other worse, but I consider that a rarity since they are all being treated by medication and therapy.