Depression is a medical illness, an illness with symptoms and a proven course of medical treatment that is effective in more than eighty percent of the cases. Depression is more than just the occasional bad mood.
Depression can be difficult to diagnose or to recognize in oneself.
The symptoms of depression easily hide behind the ordinary experience of life. We must look first at intensity. If any one symptom significantly interferes with friends, family, or work, it can indicate depression. We must also look at duration. If one has not felt pleasure for an hour, that would not indicate depression.