What type of depression is the least severe?

Depression: I have always simply explained to my patients that there were three kinds of depression, and I compared them to upper respiratory illnesses. If you have a low-level depression, it is like a cold. If you have dysthymia, it is like flu. If you have major depression, it is like pneumonia. In all cases to be diagnosed, one has to have symptoms for extended periods of time- not just a day or a week.