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 you once enjoyed. It can lead to a variety of emotional and physical problems and can decrease your 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., inability to sit still, pacing, handwringing) or slowed movements or speech (these actions must be severe enough to be observable by others).
Feeling worthless or guilty
Difficulty thinking, concentrating or making decisions
Thoughts of death or suicide