Depression (mild or major depressive disorder) is a common and serious medical illness that negatively affects how you feel, the way you think and how you act. Fortunately, it is also treatable. Depression causes feelings of sadness and/or a loss of interest in activities once enjoyed. It can lead to a variety of emotional and physical problems and can decrease a person's ability to function at work and at home. Depression symptoms can vary from mild to severe and can include:• Feeling sad or having a depressed mood• Loss of interest or pleasure in activities once enjoyed• Changes in appetite - weight loss or gain unrelated to dieting• Trouble sleeping or sleeping too much• Loss of energy or increased fatigue• Increase in purposeless physical activity (e.g., hand-wringing or pacing) or slowed movements and speech• Feeling worthless or guilty• Difficulty thinking, concentrating or making decisions• Thoughts of death or suicide• Symptoms must last at least two weeks for a diagnosis of depression.Depression is among the most treatable of mental disorders. Psychotherapy is often used in along with antidepressant medications for treatment of mild & severe depression.