Depression (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.

Depression symptoms can vary from mild to severe and can include:

1. Feeling sad or having a depressed mood
2. Loss of interest or pleasure in activities once enjoyed
3. Changes in appetite — weight loss or gain unrelated to dieting
4. Trouble sleeping or sleeping too much
5. Loss of energy or increased fatigue
6. Increase in purposeless physical activity (e.g., hand-wringing or pacing) or slowed movements and speech (actions observable by others)
7. Feeling worthless or guilty
8. Difficulty thinking, concentrating or making decisions
9. Thoughts of death or suicide