What symptoms does someone with depression always have?

Depressive symptoms: Symptoms of depression may include disturbed sleep, either difficulies initiating, or maintaining sleep, constant low feelings lasting at least 2 weeks with loss of interest in everyday activities. May include excessive guilt feelings, decreased energy, poor concentration, loss of appetite and/or weight, problems thinking clearly and possibly suicidal thoughts.

Absence of strength: Lack of joy, enthusiasm, spontaneity, initiative, energy, stamina, confidence; i see "depression" primarily as a condition that produces a flatness of emotion that robs the soul of vigor.