Experiencing sadness at one time or another is part of the normal human experience. However, depression is more than the occasional sadness that people experience. When an individual suffers from depression, the sadness tends to be more pervasive or long lasting, and can be accompanied by one or more of the following: decreased interest in pleasurable activities, feelings of hopelessness, low self-worth, excessive guilt, decrease in energy, concentration difficulties, appetite changes, sleep difficulty or excessive sleep, headaches, body aches and pains, and/or thoughts of suicide.