I didn't know that depression can be characterized in so very many ways. Somehow, I have forgotten my Psychology 11, which I took many, many, years ago.
Wikipedia says that depression could be be melancholic. It is characterized by a loss of pleasure (anhedonia) in most or all activities, a failure of reactivity to pleasurable stimuli, a quality of depressed mood more pronounced than that of grief or loss, a worsening of symptoms in the morning hours, early morning waking, psychomotor retardation, excessive weight loss (not to be confused with anorexia nervosa), or excessive guilt.
I wonder, do I have it? Periodically, I suffer from some or even most of the symptoms described. Even if I try hard to rise above the condition, it just won't go away.
I have always wanted to go to a health professional, but the cost of getting "help" might even depress me more :-)
To learn more of depression, see here and here.