I can attest to the fact that common symptoms of depression are often variable, and very often difficult to differentiate from other closely related disorders. There are a number of crossover symptoms that are common to several psychological illnesses, which sometimes makes targeted treatment difficult, and very much a process itself. I am being treated for bipolar disorder and generalized anxiety disorder. In the past my treatment focussed on depression only because, like many with bipolar, my diagnosis came late in the game. With medication, my bipolar is under control, but I was still experiencing anxiety (despite taking anti-anxiety medication) and particularly sleep disruption. I woke often during the night, and woke early, long before the alarm went off. It was only after a recent visit with my physician that it became clear that, as he put it, my depression was beginning to "break through" again in the form of one common symptom--early waking. I had assumed that being treated for bipolar would take care of everything, but apparently that is not necessarily the case. In fact, I read on this site that bipolar medication often has to be supplemented with anti-depressants. In short, I've learned that depression works like a cafeteria--you never know what will be served up that day!