Depression has been called “the common cold” of mental distress. It is estimated that over 16 million Americans experience a major depressive episode each year. This estimate does not include other depressive disorders including disruptive mood dysregulation disorder, persistent depressive disorder (dysthymia), premenstrual dysphoric disorder, substance/medication-induced depressive disorder, and depressive disorder due to another medical condition.
Common depressive symptoms include depressed mood or loss of interest or pleasure in once enjoyable activities, problems with sleep, appetite, energy, focus/concentration, self-image, or thoughts of death or suicide.
Diagnostic and statistical manual of mental disorders: DSM-5. Washington, DC: American Psychiatric Publishing, 2013.
"Major Depression." National Institute of Mental Health.
Seligman, Martin. Learned optimism: how to change your mind and your life. New York: Alfred Knopf, 2007.