Depression reflects a sad and/or irritable mood exceeding normal sadness or grief. The sadness of depression is characterized by a greater intensity and duration and by more severe symptoms and functional disabilities are more extreme than normal.

 

Signs and symptoms are characterized by negative thoughts, moods, and behaviors and also specific changes in bodily functions (crying spells, back aches, low energy or libido, problems with eating, weight or sleeping). This is because nervous system changes in the brain cause many physical symptoms resulting in diminished activity and participation.