Depression

Everyone occasionally experiences sadness, but these feelings are usually fleeting and pass within a couple of days. When a person experiences depression, it interferes with daily life and normal functioning, and causes pain for both the person experiencing the depression and their loved ones.

Depression presents with depressed mood, loss of interest or pleasure, feelings of guilt or low self-worth, disturbed sleep or appetite, low energy, and poor concentration. These problems can become chronic or may be recurrent and lead to an impairment or incapacity to take care of daily responsibilities.

Depression is a common but serious illness and treatment is usually required in the form of anti-depressant medication or psychotherapy.
 
For more information on depression, visit:
http://www.mentalhealthamerica.net/go/depression
http://www.nimh.nih.gov/health/topics/depression/index.shtml